Gypsum Board Assemblies

Revision 8 · Sep 26, 2026 +1550 −1213

SynC Standards Team — Specifier (Platform Standards) ✓ OfficialDiscloses employment SynC (SynC Platform Team)

Remade from scratch under the authoring cheatsheet: the assembly as a system built to its design number, framing and blocking owned for the trades that hang on these walls, finish levels defined, a trade-off note beside every choice

Showing changes from Rev 7 to Rev 8 in Gypsum Board Assemblies.

−---

−title: Gypsum Board Assemblies

−category: Architectural

−toc_depth: 3

−description: >

− When to use: Gypsum board partitions, wall assemblies, and ceiling systems for commercial, institutional, and multi-family residential buildings. Covers interior non-load-bearing steel-framed partitions, shaft walls, chase walls, area separation walls, furring and freestanding wall assemblies, and suspended or directly attached gypsum board ceiling systems. Includes fire-resistance-rated and sound-rated assemblies, all board types, steel framing and furring, finish levels, joint treatment, accessories, and control joints.

− Not intended for: Exterior gypsum sheathing in curtain wall or EIFS applications; gypsum board in continuously wet locations (showers, steam rooms — use tile backer systems); load-bearing cold-formed metal framing designed by a structural engineer (see [[sync/cold-formed-metal-framing]]); plaster or veneer plaster systems; firestopping at penetrations through rated assemblies (see [[sync/firestopping]]); thermal insulation within partitions (see [[sync/building-thermal-insulation]]); acoustic insulation batts (see [[sync/acoustic-insulation]]); interior painting and finishing of the completed board surface (see [[sync/interior-painting]]).

−---

−

−# Scope {toc}

−

−## This standard governs the materials, fabrication, and installation of interior gypsum board assemblies, including non-load-bearing steel-framed partitions, shaft-wall and chase-wall assemblies, area separation walls, furring assemblies, and gypsum board ceiling systems — both fire-resistance-rated and non-rated. {note}

−## Gypsum board is the dominant interior finish substrate and partition material in commercial construction because of its noncombustible core, reliable fire-resistance performance, competitive installed cost, and ease of repair. {note}

−## Properly specified and installed gypsum board assemblies also provide the acoustic separation that office buildings, healthcare facilities, hotels, and multi-family projects require. {note}

−

−## Gypsum board assemblies are systems, not products: the fire-resistance rating and acoustic performance of an assembly depend equally on the board type and thickness, the framing gauge and spacing, the number of layers, the fastener pattern, the acoustic insulation within the cavity, the perimeter treatment, and the quality of installation, and a change to any one of those variables can invalidate the rating. {note}

−

−## The Contractor shall install every rated assembly precisely as described in the applicable fire-resistance design number and as confirmed by the drawings.

−

−## The Contractor shall bring any field condition that would require a departure from the design number to the Architect of Record before proceeding.

−

−## The Contractor shall coordinate steel framing design with [[sync/cold-formed-metal-framing]] where structural performance is required.

−

−## The Contractor shall coordinate firestopping of penetrations through rated assemblies with [[sync/firestopping]].

−

−## The Contractor shall coordinate acoustic and thermal insulation batts within cavities with [[sync/acoustic-insulation]] and [[sync/building-thermal-insulation]], respectively.

−

−## The Contractor shall coordinate interior painting of finished gypsum board surfaces with [[sync/interior-painting]].

−

−# Referenced Standards {toc}

−

−## All materials, assemblies, and installation shall comply with the latest edition adopted by the Authority Having Jurisdiction for each of the following standards.

−

−| Standard | Title |

−|----------|-------|

−| ASTM C1396/C1396M | Standard Specification for Gypsum Board |

−| ASTM C840 | Standard Specification for Application and Finishing of Gypsum Board |

−| ASTM C645 | Standard Specification for Nonstructural Steel Framing Members |

−| ASTM C754 | Standard Specification for Installation of Steel Framing Members to Receive Screw-Attached Gypsum Panel Products |

−| ASTM C475/C475M | Standard Specification for Joint Compound and Joint Tape for Finishing Gypsum Board |

−| ASTM C1047 | Standard Specification for Accessories for Gypsum Wallboard and Gypsum Veneer Base |

−| ASTM C919 | Standard Practice for Use of Sealants in Acoustical Applications |

−| ASTM E119 | Standard Test Methods for Fire Tests of Building Construction and Materials |

−| ASTM E90 | Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements |

−| ASTM E413 | Classification for Rating Sound Insulation |

−| GA-216 | Application and Finishing of Gypsum Panel Products (Gypsum Association) |

−| GA-600 | Fire Resistance and Sound Control Design Manual (Gypsum Association) |

−| GA-214 | Levels of Finish for Gypsum Panel Products (Gypsum Association) |

−| IBC | International Building Code (current edition adopted by jurisdiction) |

−| UL Fire Resistance Directory | UL Fire-Resistance Rated Systems |

−

−## Where the contract documents or a referenced standard impose a more stringent requirement than the minimum of any other standard, the more stringent requirement governs unless the Architect of Record directs otherwise in writing.

−

−## The Gypsum Association GA-216 is referenced by the International Building Code for gypsum board application, so compliance is a code obligation as well as a best-practice requirement on jurisdictions that have adopted the IBC, and GA-600 provides tested fire-resistance and sound-rated assembly designs that serve as the design basis for rated construction where UL-classified assemblies are used. {note}

−

−# Submittals {toc}

−

−## Action Submittals {toc}

−

−### The Contractor shall submit the following for the Architect's review prior to procurement and installation:

−

−- Product data for each type of gypsum board, including manufacturer's physical properties, fire-test references, and applicable ASTM designations

−- Product data for steel studs, runners, furring channels, resilient channels, and all other framing and furring members, including base metal thickness, yield strength, and coating type

−- Product data for joint compound, joint tape, corner bead, trim accessories, and control joints

−- Samples of each gypsum board type proposed, minimum 12 inches × 12 inches, with edge profile visible

−- Identification of the specific UL or GA-600 fire-resistance design number for every fire-resistance-rated assembly shown on the drawings, cross-referenced to each partition type designation

−- Identification of the specific GA-600 or tested sound assembly reference number for every acoustically rated assembly, cross-referenced to partition type designations

−

−```datasheet

−label: Action Submittals Required

−type: checkbox

−options:

− - "Product data — gypsum board (all types)"

− - "Product data — steel framing and furring"

− - "Product data — joint compound and tape"

− - "Product data — trim accessories and control joints"

− - "Board samples (each type)"

− - "Fire-resistance design number schedule"

− - "Acoustic assembly reference schedule"

−default: "Product data — gypsum board (all types)"

−```

−

−### The Contractor shall submit the action submittal items listed above for the Architect's review prior to procurement and installation.

−

−### Installation of any rated assembly shall not begin until the corresponding submittals have been reviewed and returned.

−

−## Closeout Submittals {toc}

−

−### The Contractor shall provide the following at project closeout:

−

−- Warranty documentation for all gypsum board products and accessories carrying a manufacturer warranty

−- Record of any field substitution to a fire-resistance design number approved in writing by the Architect of Record, including the revised design number or engineering judgment letter from a licensed professional engineer

−

−```datasheet

−label: Closeout Submittals Required

−type: checkbox

−options:

− - "Warranty documentation for products and accessories"

− - "Record of approved fire-resistance design number substitutions"

−default: [Warranty documentation for products and accessories, Record of approved fire-resistance design number substitutions]

−```

−

−### The Contractor shall provide the closeout submittal items listed above at project closeout.

−

−# Quality Assurance {toc}

−

−## Installer Qualifications {toc}

−

−### Gypsum board installation shall be performed by workers who are experienced in commercial drywall installation of the types required on this project.

−

−### For fire-resistance-rated assemblies, workers shall be trained in the specific requirements of the rated design.

−

−### Fire-resistance performance depends on the precise execution of fastener patterns, framing gauge, joint treatment, and perimeter conditions, and workers who are unaware of the design constraints cannot meet them. {note}

−

−## Pre-Installation Conference {toc}

−

−### Before gypsum board installation begins, the Contractor shall hold a pre-installation conference with the Owner's representative and the Architect to review the fire-resistance design schedule, the acoustic assembly schedule, the finish level schedule, and any special conditions shown on the drawings.

−

−### Departures from any fire-resistance design number shall be resolved at or before this conference, not in the field.

−

−## Mock-Up {toc}

−

−```datasheet

−label: Mock-Up Required

−type: radio

−options:

− - "Yes — one representative partition per rated type"

− - "No"

−default: "No"

−```

−

−### Where the contract documents require a mock-up, the Contractor shall construct one representative partition of each rated partition type at a location directed by the Architect.

−

−### The mock-up shall remain in place for review before the production installation proceeds.

−

−### The mock-up shall demonstrate the framing layout, board type and thickness, fastener pattern, perimeter relief, control joint detail, and finish level.

−

−## Field Inspection of Rated Assemblies {toc}

−

−### The Authority Having Jurisdiction and the Owner's representative shall have the right to inspect rated assemblies before they are covered by finishes.

−

−### The Contractor shall not cover any fire-resistance-rated or acoustically rated assembly until it has been inspected and approved or until written permission to proceed has been issued.

−

−## Testing Agency {toc}

−

−```datasheet

−label: Field Acoustic Testing Required

−type: radio

−options:

− - "Yes — by independent accredited testing agency"

− - "No"

−default: "No"

−```

−

−### Where sound transmission class or impact isolation class verification testing is specified, an independent accredited testing agency shall perform field measurements in accordance with ASTM E336 and ASTM E597 and shall issue test reports to the Owner.

−

−# Environmental Conditions {toc}

−

−## Temperature and Humidity During Application {toc}

−

−```datasheet

−label: Minimum Ambient Temperature During Installation and Finishing

−type: range

−unit: °F

−options:

− min: 55

− max: 65

− step: 5

−default: 55

−```

−

−### Gypsum board installation, joint treatment, and finishing shall not proceed when ambient air temperature or substrate temperature is below 55 °F (13 °C) or above 95 °F (35 °C) unless temporary heat and ventilation are provided to maintain acceptable conditions.

−

−### Temperatures shall be maintained throughout the application and drying period.

−

−### Rapid temperature fluctuations shall be avoided, because they cause differential thermal movement that can crack freshly dried joint compound before it has fully cured.

−

−### Joint treatment products require moisture in the gypsum core and at the paper face to bond and cure properly, and both extremes — excessively dry conditions and excessively humid conditions — impair the quality of the finished joint; in winter, temporary heat sources that consume moisture from the air can produce conditions that are too dry for joint compound to cure uniformly, leading to shrinkage cracking and poor bond. {note}

−

−## Ventilation {toc}

−

−### Adequate ventilation shall be provided to remove excess moisture during installation and through the complete drying of joint compound.

−

−### Mechanical ventilation or forced-air circulation shall be used when natural ventilation is insufficient to accomplish this within the project schedule.

−

−### Stagnant air traps moisture over freshly applied compound and produces slow, uneven drying, which can cause blisters, ridging, and bond failures. {note}

−

−## Moisture Content of Framing {toc}

−

−### Steel framing for gypsum board shall be free of corrosion and shall not be in contact with materials containing moisture that could accelerate corrosion.

−

−### Where conditions indicate high moisture exposure during construction — for example, following a wet concrete pour in a space with limited drying — steel framing shall be allowed to dry and any surface rust cleaned before board is applied.

−

−## Protection of Installed Board {toc}

−

−### Installed gypsum board shall be protected from direct water contact, prolonged moisture exposure, and physical damage until the building is enclosed and climate-controlled.

−

−### Gypsum board that has been wetted shall be inspected before finishing.

−

−### Board with surface paper separation, warping, or core softening shall be replaced.

−

−# Gypsum Board Materials {toc}

−

−## General Product Requirements {toc}

−

−### All gypsum board shall conform to ASTM C1396/C1396M.

−

−### Every board shall bear the manufacturer's label, the ASTM standard designation, and the type designation.

−

−### Board arriving on site without legible markings shall be rejected.

−

−### The gypsum core shall be essentially non-combustible per the ASTM standard, and the paper faces shall be bonded to the core for the full extent of the board.

−

−## Regular Gypsum Board {toc}

−

−### Regular gypsum board is the baseline product defined in ASTM C1396 for interior wall and ceiling applications where fire resistance is not required and moisture resistance is not a primary concern. {note}

−### It is the most economical board type and is appropriate for the majority of interior office, retail, and light commercial applications. {note}

−

−### The thickness of regular gypsum board shall be specified for each application.

−

−```datasheet

−label: Regular Gypsum Board Thickness

−type: radio

−unit: in

−options:

− - "1/4 in"

− - "3/8 in"

− - "1/2 in"

− - "5/8 in"

−drawing_ref: true

−default: "1/2 in"

−```

−

−### The edge profile of regular gypsum board shall be specified to suit the intended finishing method.

−

−```datasheet

−label: Regular Gypsum Board Edge Profile

−type: radio

−options:

− - "Tapered (standard for two-coat finishing)"

− - "Square edge (for surface-applied textures or tile base)"

− - "Beveled"

− - "Rounded"

−default: "Tapered (standard for two-coat finishing)"

−```

−

−### Regular gypsum board is not formulated with fire-resistant additives and shall not be substituted for Type X board in fire-resistance-rated assemblies.

−

−## Type X Gypsum Board {toc}

−

−### Type X gypsum board is defined in ASTM C1396 as a board that achieves a fire resistance of not less than one hour for 5/8-inch thickness and not less than 45 minutes for 1/2-inch thickness when tested in accordance with ASTM E119 in a specific assembly. {note}

−### The 5/8-inch Type X board is the standard board for fire-resistance-rated gypsum board assemblies in commercial construction and is the most common board type required by fire-resistance design numbers. {note}

−

−### Type X achieves its fire resistance through special core additives — typically glass fibers — that maintain core integrity and slow heat transmission, and the fire-resistance rating of an assembly using Type X board is a property of the entire assembly because the board alone does not carry a rating. {note}

−

−### The Contractor shall verify that the board, framing, fastener pattern, and all other assembly variables match the cited fire-resistance design number precisely.

−

−```datasheet

−label: Type X Gypsum Board Thickness

−type: radio

−unit: in

−options:

− - "1/2 in (45-minute assemblies)"

− - "5/8 in (one-hour and multi-hour assemblies)"

−drawing_ref: true

−default: "5/8 in (one-hour and multi-hour assemblies)"

−```

−

−## Type C Gypsum Board {toc}

−

−### Type C gypsum board is a proprietary formulation that meets and exceeds the ASTM C1396 Type X requirements. {note}

−### Type C panels contain shrinkage-compensating additives — typically vermiculite — that cause the core to expand slightly when exposed to fire, maintaining joint integrity and extending fire resistance beyond what Type X achieves. {note}

−### All Type C products also qualify as Type X, but Type X products do not qualify as Type C. Type C is required by certain GA-600 and UL fire-resistance design numbers that demand longer fire ratings (commonly two hours) at thinner board profiles than Type X can achieve. {note}

−

−### The Contractor shall not substitute Type X for Type C in assemblies where the design number specifically calls for Type C, because the expansion behavior that maintains joint integrity under prolonged fire exposure is specific to the Type C formulation.

−

−```datasheet

−label: Type C Board Required

−type: radio

−options:

− - "Yes — assembly design number calls for Type C"

− - "No — Type X is sufficient"

−drawing_ref: true

−default: "No — Type X is sufficient"

−```

−

−## Moisture- and Mold-Resistant Gypsum Board {toc}

−

−### Moisture-resistant gypsum board is formulated for use in areas subject to intermittent moisture exposure — bathrooms adjacent to tiled showers, break rooms, locker rooms, and similar spaces where moisture is present but standing water is not. {note}

−### The product designation under ASTM C1396 requires both reduced water absorption of the core and reduced surface water absorption of the paper facing. {note}

−### Mold-resistant products additionally contain biocidal additives in the core and face paper to resist mold and mildew growth under elevated humidity conditions. {note}

−

−### The core designation of moisture- and mold-resistant gypsum board shall be specified based on the humidity and mold-exposure conditions of the space.

−

−```datasheet

−label: Moisture/Mold-Resistant Board — Core Designation

−type: radio

−options:

− - "Standard moisture resistant (meets ASTM C1396 water absorption requirements)"

− - "Mold resistant (treated core and face paper)"

− - "Not required"

−drawing_ref: true

−default: "Mold resistant (treated core and face paper)"

−```

−

−### Moisture-resistant board shall not be used as a tile backer in continuously wet areas such as shower enclosures or steam rooms.

−

−### Continuously wet tile backer applications require cement board, glass-mat tile backer, or fiber-cement backer products. {note}

−

−## Glass-Mat Gypsum Board {toc}

−

−### Glass-mat gypsum board replaces the paper facing with a glass-fiber mat embedded in and bonded to the core. {note}

−### The glass-mat facing is inherently resistant to moisture, mold, and mildew because it contains no organic material for mold to consume. {note}

−### Glass-mat boards are appropriate for high-humidity environments, behind tile in wet areas above grade, and for exterior-facing applications such as gypsum sheathing that will be exposed during construction. {note}

−

−### Glass-mat boards designated for interior use differ from glass-mat sheathing in their surface texture, coating, and edge treatment, and the two product types are not interchangeable. {note}

−

−### In high-humidity interior locations, glass-mat board provides a more robust moisture-resistance performance than paper-faced moisture-resistant board and should be specified wherever the consequences of mold contamination are serious — healthcare, hospitality, and occupied multi-family.

−

−```datasheet

−label: Glass-Mat Gypsum Board

−type: radio

−options:

− - "Required — interior glass-mat type"

− - "Not required"

−drawing_ref: true

−default: "Not required"

−```

−

−## Impact- and Abuse-Resistant Gypsum Board {toc}

−

−### Abuse-resistant and impact-resistant gypsum board products have reinforced cores — typically higher-density gypsum with glass fiber and polymer additives — and reinforced face papers that resist dents, scuffs, and penetration better than standard board. {note}

−### They are appropriate in corridors, stairwells, gymnasiums, activity rooms, healthcare support spaces, and other areas where the wall surface will be subject to carts, equipment, rolling loads, and physical contact. {note}

−

−### Abuse- or impact-resistant gypsum board and its required performance level shall be specified where the wall surface will be subject to carts, equipment, or physical contact.

−

−```datasheet

−label: Abuse/Impact-Resistant Board

−type: radio

−options:

− - "Required — high-abuse type (densified core, reinforced face)"

− - "Required — moderate-abuse type"

− - "Not required"

−drawing_ref: true

−default: "Not required"

−```

−

−### The board type alone does not determine abuse resistance; the framing gauge, stud spacing, number of layers, and base layer attachment also contribute. {note}

−

−### The Contractor shall confirm that the complete assembly matches the intended performance level.

−

−## Shaftliner and Coreboard {toc}

−

−### Shaftliner board is a 1-inch-thick gypsum board with a specially formulated dense core designed for use in 2-inch-deep H-stud shaft-wall assemblies and area separation walls. {note}

−### Shaftliner is installed without framing on its back side — it is captured between I- or H-shaped steel studs and bears against the steel directly. {note}

−### Its density and thickness allow it to perform structurally in this configuration without supplemental framing on the cavity-facing side. {note}

−### Shaftliner board is a Type X designation product whose specific fire-resistance performance is established by the tested assembly design, not by a standalone product rating. {note}

−### Coreboard is a related product in 1-inch thickness used in solid or laminated solid-core partition systems; its application is limited to specific design configurations. {note}

−

−### Whether shaftliner board is required for an H-stud shaft wall assembly shall be specified for each applicable partition configuration.

−

−```datasheet

−label: Shaftliner Board Required

−type: radio

−options:

− - "Yes — 1-inch Type X shaftliner for H-stud shaft wall assembly"

− - "No"

−drawing_ref: true

−default: "No"

−```

−

−## Board Dimensions {toc}

−

−```datasheet

−label: Board Width

−type: radio

−unit: in

−options:

− - "48 in (standard)"

− - "54 in"

−default: "48 in (standard)"

−```

−

−```datasheet

−label: Board Length

−type: select

−unit: ft

−options:

− - "8 ft"

− - "9 ft"

− - "10 ft"

− - "12 ft"

− - "14 ft"

− - "16 ft"

−drawing_ref: true

−default: "10 ft"

−```

−

−### Boards shall be cut to minimize joints and to allow horizontal orientation of boards on walls where the assembly height makes it practical.

−

−### Where boards must be oriented vertically, butt joints between non-tapered ends shall be back-blocked to provide a stiff substrate for joint treatment.

−

−### Horizontal orientation reduces the number of butt-end joints, which are the most difficult to finish invisibly because horizontal joints occur at tapered edges. {note}

−

−# Steel Framing and Furring {toc}

−

−## General Framing Requirements {toc}

−

−### All nonstructural steel framing and furring members shall conform to ASTM C645.

−

−### Installation shall conform to ASTM C754 and GA-216.

−

−### The Contractor shall not attach hangers, mechanical equipment, or structural loads to nonstructural steel framing without Engineer of Record approval.

−

−### Steel framing for gypsum board assemblies is non-load-bearing — it is designed to carry the self-weight of the gypsum board and to resist lateral loads (wind load on exterior curtain partitions, seismic drift at full-height partitions) but is not designed to carry vertical structural loads. {note}

−

−### Full-height partitions that extend to the structural deck above shall be provided with deflection heads — slip-track or similar top-runner details — that allow the structure to deflect vertically without transferring load into the partition and without cracking the gypsum board at the top of the partition.

−

−### The deflection head detail shall be shown on the drawings and the Contractor shall execute it precisely, because a partition that is structurally loaded at its top will crack at the ceiling line even if the board is otherwise perfectly installed.

−

−## Steel Stud Width {toc}

−

−```datasheet

−label: Steel Stud Width (Nominal)

−type: select

−unit: in

−options:

− - "1-5/8 in (T-bar partition, extremely limited use)"

− - "2-1/2 in"

− - "3-5/8 in"

− - "4 in"

− - "6 in"

−drawing_ref: true

−default: "3-5/8 in"

−```

−

−### For partitions requiring high STC ratings (above STC 50), the wall cavity width and the type of framing — whether single-stud, double-stud, or staggered-stud — are critical design variables and shall be coordinated with the acoustic assembly reference number.

−

−### The stud width determines the cavity depth available for acoustic insulation, the separation between wall faces (which affects STC), and the flexural stiffness of the partition, so wider studs generally produce stiffer and better-performing acoustic assemblies. {note}

−

−## Steel Stud Gauge {toc}

−

−### Nonstructural steel studs are available in 25-gauge (25 mil base metal thickness per ASTM C645), 20-gauge, 18-gauge, and heavier sections. {note}

−### The 25-gauge (20-mil delivered product minimum per ASTM C645) is the minimum conforming gauge for interior gypsum board partitions. {note}

−### For typical commercial partitions up to 10 feet in height under normal lateral loading, 25-gauge studs at 16 inches on center are often acceptable; partitions over 12 feet in height, or partitions subject to elevated lateral loads such as those adjacent to exterior walls in high-wind zones, require heavier gauge. {note}

−

−### The steel stud gauge shall be specified based on the partition height and the lateral loading it will be subject to.

−

−```datasheet

−label: Steel Stud Gauge

−type: select

−options:

− - "25 gauge (20 mil delivered, 33 ksi min)"

− - "20 gauge (30 mil delivered)"

− - "18 gauge (43 mil delivered)"

− - "16 gauge (54 mil delivered)"

−drawing_ref: true

−default: "25 gauge (20 mil delivered, 33 ksi min)"

−```

−

−### The Contractor shall not substitute 25-gauge studs for heavier gauge specified on the drawings without the Engineer of Record's approval.

−

−### EQ studs meeting the minimum ASTM C645 requirements are acceptable; EQ studs that do not meet ASTM C645 minimum thickness requirements are not acceptable regardless of yield strength unless specifically designed and approved.

−

−### A common field error is the use of equivalent-gauge (EQ) studs, which achieve a given minimum moment of inertia through a combination of thinner steel and higher yield strength rather than the same steel thickness as the nominal gauge. {note}

−

−### Stud gauge determines the load-carrying capacity, stiffness, and height of the partition. {note}

−

−## Stud Spacing {toc}

−

−```datasheet

−label: Stud Spacing

−type: select

−unit: in o.c.

−options:

− - "12 in o.c."

− - "16 in o.c."

− - "24 in o.c."

−drawing_ref: true

−default: "16 in o.c."

−```

−

−### For single-layer board applications, studs at 16 inches on center are standard; 24 inches on center is acceptable for lightweight partitions under limited height and loading conditions and where the board thickness and fastener pattern are adjusted accordingly.

−

−### Acoustic assemblies using resilient channel attachment of the gypsum board may require closer stud spacing to avoid excess deflection at the channel span.

−

−### Stud spacing affects the spanning capacity of the framing, the stiffness of the partition, and the fastener pattern of the gypsum board. {note}

−

−## Runners and Bridging {toc}

−

−### Top and bottom runners shall be the same width as the studs and shall conform to ASTM C645.

−

−### Bottom runners shall be anchored to the floor slab at intervals not exceeding 24 inches on center and at each end of the run.

−

−### Top runners for full-height partitions extending to the structure shall be anchored to the deck assembly.

−

−### Deflection head top runners used in lieu of fixed top runners shall have a minimum 2-inch leg depth that allows the stud top to slide vertically within the track by at least 3/4 inch to accommodate structural deflection, with the amount of slop confirmed against the structural deflection indicated on the drawings.

−

−### Bridging or bracing of studs shall be installed per ASTM C754 at intervals not exceeding the ASTM C754 span tables for the gauge and spacing selected, and additionally at all locations where the partition height-to-width ratio makes lateral bracing necessary for stability during construction.

−

−### Bridging channels shall be fastened to each stud with two approved fasteners.

−

−## Furring Channels {toc}

−

−### Furring channels — hat-shaped channels and resilient channels — are used to attach gypsum board to masonry or concrete substrates, to provide a cavity for mechanical and electrical runs, and, in the case of resilient channels, to acoustically decouple the gypsum board from the framing to improve sound isolation. {note}

−

−### The furring channel type shall be specified based on the substrate attachment and acoustic decoupling requirements of the assembly.

−

−```datasheet

−label: Furring Channel Type

−type: radio

−options:

− - "Hat channel (rigid — direct attachment to substrate)"

− - "Resilient channel (flexible — acoustic decoupling from framing)"

− - "Not applicable"

−drawing_ref: true

−default: "Hat channel (rigid — direct attachment to substrate)"

−```

−

−### Furring channel installation shall conform to ASTM C754 and to the applicable fire-resistance design number where furring is part of a rated assembly.

−

−### The Contractor shall use the correct screw length for each layer of board and shall verify that screws used to attach gypsum board to resilient channel do not contact the stud below.

−

−### The furring channel shall be fastened to the stud with a self-drilling screw, and the board shall be attached to the channel with a screw that engages only the channel.

−

−### The single most common error with resilient-channel assemblies is short-circuiting — fastening the gypsum board through the resilient channel and into the framing below with a screw that is too long — which bypasses the channel's resilience and can drop the STC of the assembly by 10 to 15 points. {note}

−

−## Cold-Formed Metal Framing for Structural Partitions {toc}

−

−### Where partitions carry structural loads — floor-to-floor corridor walls, shear walls designed with gypsum board as a structural sheathing element, or other load-bearing applications — the framing design shall be prepared by a licensed structural engineer and the framing shall conform to [[sync/cold-formed-metal-framing]].

−

−### This standard does not govern structural cold-formed framing. {note}

−

−# Fire-Resistance-Rated Assemblies {toc}

−

−## General Fire-Resistance Requirements {toc}

−

−```datasheet

−label: Fire-Resistance Design Source

−type: radio

−options:

− - "UL Fire-Resistance Directory"

− - "GA-600 Fire Resistance and Sound Control Design Manual"

− - "Other tested assembly — approved engineering judgment"

−drawing_ref: true

−default: "UL Fire-Resistance Directory"

−```

−

−```datasheet

−label: Required Fire-Resistance Rating

−type: select

−unit: hours

−drawing_ref: true

−options:

− - "Not rated"

− - "45 minutes"

− - "1 hour"

− - "1.5 hours"

− - "2 hours"

− - "3 hours"

− - "4 hours"

−default: "1 hour"

−```

−

−### Fire-resistance-rated gypsum board assemblies shall be constructed in strict conformance with a tested fire-resistance design.

−

−### The fire-resistance rating of an assembly is a property of the entire system as tested — substituting a different board type, changing framing gauge or spacing, altering fastener patterns, changing insulation, or modifying perimeter conditions can invalidate the rating, and the tested design is the contract, not the fire-resistance rating number in isolation. {note}

−

−### Tested fire-resistance designs shall be obtained from UL Fire-Resistance Directory (UL assemblies) or from GA-600 (Gypsum Association designs), both of which are accepted by the International Building Code.

−

−### The design number shall be listed in the partition type schedule on the drawings and in the submittal.

−

−### The Contractor shall verify that the proposed materials conform to every requirement of the design number, including proprietary requirements if any, before procurement.

−

−## Common Fire-Resistance-Rated Assembly Configurations {toc}

−

−### One-hour rated partitions in commercial construction are typically achieved with a single layer of 5/8-inch Type X gypsum board on each side of 25-gauge steel studs at 16 or 24 inches on center, with runners anchored to the structure. {note}

−### The joint treatment and fastener pattern are as specified in the design number. {note}

−### Two-hour ratings commonly require two layers of 5/8-inch Type X board on one or both sides, or one layer of Type C board on each side of a specific framing configuration. {note}

−### Area separation walls and shaft walls use 1-inch shaftliner panels captured in H- or I-studs combined with Type X face layers. {note}

−

−### The number of gypsum board layers on the fire-exposed side of the assembly shall be specified per the governing fire-resistance design number.

−

−```datasheet

−label: Number of Board Layers — Fire-Exposed Side

−type: select

−drawing_ref: true

−options:

− - "Single layer"

− - "Double layer"

− - "Per design number — asymmetric layers"

−default: "Single layer"

−```

−

−### The number of gypsum board layers on the non-fire-exposed side of the assembly shall be specified per the governing fire-resistance design number.

−

−```datasheet

−label: Number of Board Layers — Non-Fire-Exposed Side

−type: select

−drawing_ref: true

−options:

− - "Single layer"

− - "Double layer"

− - "Per design number"

−default: "Single layer"

−```

−

−### The specific fire resistance of a gypsum board assembly depends primarily on the number and type of gypsum board layers on the fire-exposed side, because gypsum calcination — the release of chemically bound water from the gypsum dihydrate — is what absorbs heat and delays temperature rise on the unexposed side; the gypsum dehydration process consumes approximately 850 BTU per pound of gypsum at temperatures between 212 °F and 400 °F, providing a substantial thermal sink, and once the calcination front passes through the board thickness, protection is lost rapidly. {note}

−

−## Perimeter and Head-of-Wall Conditions for Rated Assemblies {toc}

−

−### The head-of-wall joint at the top of a fire-resistance-rated partition is among the most frequently cited deficiencies in construction inspections. {note}

−### A gap or an improperly filled joint at the top of a rated partition creates a direct air path that negates the fire rating. {note}

−

−### The head-of-wall condition — whether the partition runs to a fixed deck or to a deflection head — shall be detailed on the drawings and shall be executed as shown.

−

−```datasheet

−label: Head-of-Wall Fire-Rating Detail

−type: radio

−options:

− - "Fixed top — partition at structure, joint sealed with rated sealant"

− - "Deflection head — slip track with rated flexible joint per design number"

−drawing_ref: true

−default: "Deflection head — slip track with rated flexible joint per design number"

−```

−

−### Where a deflection head detail is used, the joint between the top of the gypsum board and the underside of the deck or ceiling above shall be filled with a listed intumescent sealant or equivalent fire-rated flexible joint system that accommodates the design deflection movement while maintaining the fire rating throughout the life of the building.

−

−### The Contractor shall confirm that the selected head-of-wall detail has been tested or evaluated for the deflection amount indicated on the drawings.

−

−### Consult [[sync/firestopping]] for penetrations through the assembly; this standard governs only the assembly itself and its perimeter conditions. {note}

−

−## Shaft-Wall and Chase-Wall Assemblies {toc}

−

−### Shaft walls enclose elevator shafts, stair shafts, mechanical chases, and other vertical openings that penetrate multiple floors. {note}

−### They must provide both the required fire resistance — typically two hours for commercial buildings per IBC requirements for elevator and stair shafts — and the structural capacity to span floor-to-floor without framing on both sides of the panel, because the inside of the shaft is not accessible for framing after construction.

−

−```datasheet

−label: Shaft-Wall Configuration

−type: radio

−options:

− - "C-H stud (shaftliner panels in channel, Type X face layers at studs)"

− - "I-stud area separation wall"

− - "Not applicable"

−drawing_ref: true

−default: "Not applicable"

−```

−### Shaft walls use 1-inch shaftliner panels installed horizontally between I-shaped or C-H steel studs anchored to the floor and ceiling runners, with Type X face layers applied to the stud faces on the accessible side. {note}

−

−### Any damage to shaftliner panels during installation — cracking, crushing of the edge, or improper fit in the stud channel — shall cause rejection and replacement of the affected panel, because damaged panels may not carry the design lateral load or maintain the fire-resistance rating.

−

−### The structural performance of a shaft-wall assembly depends on the mechanical interlock between the shaftliner panel and the steel stud, and on the fastening of the face layer to the stud. {note}

−

−## Area Separation Walls {toc}

−

−### Area separation walls provide fire resistance between separate dwelling units or fire areas in multi-family and mixed-use construction. {note}

−### Because area separation walls must survive even if the construction on one side collapses, they are designed as freestanding assemblies using I-studs and shaftliner panels with a continuous gypsum board core that does not rely on the adjacent framing for support.

−### Each unit's framing is attached to the area separation wall with a breakaway clip that allows the framing to collapse away from the wall without pulling the wall down. {note}

−

−# Acoustic Assemblies {toc}

−

−## General Acoustic Requirements {toc}

−

−### Acoustic performance of gypsum board partitions is characterized by the Sound Transmission Class (STC) for airborne sound per ASTM E413 and ASTM E90. {note}

−### The STC is a single-number rating derived from laboratory measurements; higher numbers indicate better sound isolation. {note}

−### Field performance measured per ASTM E336 (Field Sound Transmission Class, FSTC) typically runs 3 to 5 STC points below laboratory performance due to flanking paths, construction variations, and penetrations. {note}

−

−### The Architect shall specify the required STC for each partition type, taking into account the design goal (occupant privacy, program adjacency, HIPAA or similar requirements), the available wall cavity depth, and the acceptable construction cost.

−

−```datasheet

−label: Required STC Rating

−type: select

−drawing_ref: true

−options:

− - "Not rated"

− - "STC 35 (basic separation)"

− - "STC 40"

− - "STC 45"

− - "STC 50"

− - "STC 55"

− - "STC 60+"

−default: "STC 45"

−```

−

−### Specifying STC without specifying the assembly design number or without coordinating framing, insulation, and perimeter sealing leaves the performance undefined, because the Contractor may build a compliant-looking assembly that does not achieve the rated STC when one or more critical details is missing. {note}

−

−## Acoustic Assembly Design Reference {toc}

−

−```datasheet

−label: Acoustic Assembly Reference Number

−type: radio

−options:

− - "GA-600 sound-rated design"

− - "Published laboratory test report"

− - "No rating required"

−drawing_ref: true

−default: "GA-600 sound-rated design"

−```

−

−## Framing for Acoustic Assemblies {toc}

−

−### Standard single-stud construction with gypsum board directly fastened to both sides of the studs provides moderate sound isolation — typically STC 35 to 45 depending on stud depth, board layers, and cavity insulation. {note}

−### Higher STC ratings generally require one of the following approaches: resilient channel on one or both sides to acoustically decouple the board from the framing; double-stud framing with a continuous air gap between the two stud rows and no physical connection between them; or staggered-stud framing on a common base plate with board alternating between the two stud rows. {note}

−### Each approach raises cost and assembly thickness but can achieve STC values above 55 in tested configurations. {note}

−

−### Regardless of the framing type, acoustic performance depends on eliminating flanking paths — the paths by which sound bypasses the partition through the structure, through penetrations, or through gaps in the perimeter sealing. {note}

−

−### A well-framed high-STC partition that is not perimeter-sealed, or that has back-to-back electrical boxes in the same stud bay, will perform at STC values far below its laboratory rating, and flanking is the single most common cause of acoustic failures in field measurements. {note}

−

−## Acoustic Insulation in Cavities {toc}

−

−### Acoustic insulation shall be installed in the cavity of all acoustically rated partitions.

−

−### The insulation type and thickness shall match the tested assembly exactly.

−

−### Acoustic mineral fiber or glass fiber batt insulation shall fill the cavity from runner to runner and from stud to stud without compression or gaps.

−

−### Insulation installation shall be coordinated with [[sync/acoustic-insulation]].

−

−### Insulation that is compressed, torn, or installed with gaps provides less benefit than fully installed insulation and can actually reduce STC by altering the cavity resonance. {note}

−

−## Acoustic Sealant {toc}

−

−```datasheet

−label: Acoustic Sealant Applied at Perimeter

−type: radio

−options:

− - "Yes — ASTM C919 sealant at all perimeter conditions"

− - "No — not an acoustically rated partition"

−drawing_ref: true

−default: "Yes — ASTM C919 sealant at all perimeter conditions"

−```

−

−### Acoustic sealant shall be applied to all perimeter conditions of acoustically rated partitions in accordance with ASTM C919.

−

−### All gaps and openings at the floor runner, the top runner or head-of-wall joint, and the perimeter of each face of the partition at adjacent walls, columns, and structure shall be sealed with acoustic sealant before applying the final layer of gypsum board.

−

−### The sealant shall be a permanently flexible, non-hardening, non-staining type formulated for acoustic applications; conventional caulk that hardens over time shall not be used because hardened sealant transmits vibration rather than isolating it.

−

−## Electrical Boxes in Acoustic Partitions {toc}

−

−### Electrical boxes are one of the most reliable sources of acoustic flanking failures in commercial construction. {note}

−### Back-to-back electrical boxes installed in the same stud bay provide a direct acoustic path through the partition because only the thin panel of gypsum board and the box depth separate the two cavities. {note}

−

−### Back-to-back boxes shall not be installed in the same stud bay in any acoustically rated partition.

−

−### Boxes shall be offset a minimum of 24 inches horizontally in the partition.

−

−### In high-STC applications, all boxes shall be provided with pre-formed acoustic putty pads or listed acoustic box covers that seal the box perimeter and the knockout openings.

−

−```datasheet

−label: Electrical Box Treatment in Acoustic Partitions

−type: radio

−options:

− - "Boxes offset minimum 24 in — no back-to-back in same bay"

− - "Boxes offset and provided with acoustic putty pads or covers"

− - "Not applicable — partition is not acoustically rated"

−drawing_ref: true

−default: "Boxes offset minimum 24 in — no back-to-back in same bay"

−```

−

−# Accessories and Trim {toc}

−

−## General Accessories Requirements {toc}

−

−### All accessories — corner bead, edge trim, casing bead, control joints, and reveal beads — shall conform to ASTM C1047.

−

−### Accessories shall be compatible with the gypsum board and joint compound system.

−

−### Accessories of different metals shall not be combined in a way that creates a galvanic couple in a moist environment.

−

−### In areas of high humidity, accessories shall be fabricated from hot-dipped galvanized steel, rigid PVC, or rolled zinc alloy to resist corrosion.

−

−## Corner Bead {toc}

−

−```datasheet

−label: Corner Bead Type

−type: radio

−options:

− - "Metal — crimped or nailed attachment"

− - "Metal — clip-on attachment"

− - "Paper-faced metal"

− - "Vinyl/PVC"

−default: "Paper-faced metal"

−```

−

−### Corner bead shall be installed at all exterior corners of gypsum board assemblies to reinforce the corner edge against impact and to provide a straight, consistent surface for finishing.

−

−### Paper-faced metal corner bead is preferred for standard finish applications because the paper face bonds to the joint compound and reduces the tendency for bead cracking at the nose when the corner is subject to minor impacts; metal corner bead provides the most impact-resistant nose protection and is appropriate in locations where the corner will be subject to physical contact, and vinyl bead is suitable where corrosion resistance is required and impact is limited. {note}

−

−## L-Bead and Trim Bead {toc}

−

−```datasheet

−label: Casing Bead / L-Bead Material

−type: radio

−options:

− - "Galvanized steel"

− - "Zinc alloy"

− - "PVC"

−default: "Zinc alloy"

−```

−

−### L-bead (casing bead) shall be installed wherever the gypsum board terminates against a dissimilar material — at door frames, window frames, columns, masonry walls, and at any edge that is not covered by corner bead and cannot be finished as a tapered joint.

−

−### L-bead provides a clean termination line and protects the board edge from damage during and after construction. {note}

−

−## Reveal and Shadow-Line Beads {toc}

−

−### Reveal beads and shadow-line beads are installed where a recessed joint or shadow line is desired at partition terminations, at changes in plane, or as a design element at ceiling lines and wall bases.

−

−### Reveal and shadow-line beads shall be installed plumb and level, attached per the manufacturer's instructions, and finished to the same level as the adjacent gypsum board.

−

−## Control Joint Beads {toc}

−

−```datasheet

−label: Control Joint Profile

−type: radio

−options:

− - "Standard V-groove — 1/4 in reveal"

− - "Standard V-groove — 1/8 in reveal"

− - "Flat face (flush profile)"

−default: "Standard V-groove — 1/4 in reveal"

−```

−

−### Control joints shall be installed wherever required to prevent cracking caused by differential movement of the gypsum board assembly.

−

−### Control joints shall be a listed, pre-formed metal or vinyl section that creates a continuous, sealed break in the gypsum board face — they are not simply a taped joint or a scored break in the board face.

−

−### Both wings of the control joint shall be embedded in or attached to the gypsum board surface, and the exposed spine of the joint shall remain free from joint compound so that the joint can move.

−

−### Painting over or filling the control joint spine with compound defeats its purpose and will cause the board to crack at some other location. {note}

−

−# Joint Treatment and Finish Levels {toc}

−

−## General Joint Treatment Requirements {toc}

−

−### Joint treatment shall conform to ASTM C840 and GA-216.

−

−### Joint compound shall conform to ASTM C475/C475M.

−

−### All tapered joints, butt joints, interior angles, fastener heads, and accessory flanges shall receive joint treatment appropriate to the specified finish level.

−

−### Joint treatment shall not be applied when the ambient temperature is below 55 °F, because joint compound does not cure properly at low temperatures and will crack during drying.

−

−## Joint Compound Types {toc}

−

−### Joint compound is available in setting-type (chemical-hardening) and drying-type (evaporative-hardening) formulations, each appropriate for different applications. {note}

−### Setting-type compound hardens by a chemical reaction between the gypsum powder and water and reaches full hardness regardless of temperature or humidity — it is appropriate for embedding tape in the first coat, for filling deep voids and back-blocking, and for patching in cold conditions. {note}

−### Setting-type compound is harder to sand and must be applied carefully because it cannot be reworked once it begins to set.

−### Drying-type compound is used for finish coats because it is lighter, sands more easily, and produces a smoother surface; it cannot be applied in thick coats without shrinkage cracking and is not suitable for embedding tape in high-humidity conditions. {note}

−

−### The joint compound type used for the tape embedding coat shall be specified, and drying-type compound shall not be used to embed tape in high-humidity conditions.

−

−```datasheet

−label: Tape Embedding Coat Compound Type

−type: radio

−options:

− - "Setting-type (chemical hardening)"

− - "Drying-type (all-purpose or taping compound)"

−default: "Setting-type (chemical hardening)"

−```

−

−### The joint compound type used for the finish coat shall be specified.

−

−```datasheet

−label: Finish Coat Compound Type

−type: radio

−options:

− - "Drying-type topping compound"

− - "Drying-type all-purpose compound"

− - "Setting-type finish compound"

−default: "Drying-type topping compound"

−```

−

−## Joint Tape {toc}

−

−### Paper joint tape is the standard tape for flat joints and interior angles and produces the flattest finished surface when properly applied. {note}

−### Fiberglass mesh tape has higher tensile strength but requires setting-type compound for adequate bond; it is more appropriate for patching and for joints in wet areas. {note}

−### Paper tape embedded in setting-type compound at the first coat with finish coats of drying-type topping compound is the standard sequence for commercial construction. {note}

−

−### Joint tape shall conform to ASTM C475/C475M.

−

−```datasheet

−label: Joint Tape Type

−type: radio

−options:

− - "Paper tape (standard for flat joints)"

− - "Fiberglass mesh tape (setting compound required)"

−default: "Paper tape (standard for flat joints)"

−```

−

−## Levels of Finish {toc}

−

−### The Gypsum Association GA-214 defines six levels of finish for gypsum board, numbered 0 through 5. {note}

−### The appropriate finish level depends on the final decoration and the lighting conditions at the surface. {note}

−### Specifying the correct finish level is one of the most important decisions in gypsum board specification because it defines the cost and quality of the finishing work, and because disputes over finish quality are among the most common construction disputes on commercial interior projects. {note}

−

−### **Level 0:** No finishing required. {note}

−- Typically reserved for temporary construction or spaces where the final decoration has not been determined.

−- No tape, compound, or accessories required.

−

−### **Level 1:** Tape embedded in joint compound at all joints and interior angles. {note}

−- Excess compound and tool marks acceptable.

−- For plenum areas above ceilings, attics, and areas concealed from normal view.

−- Fire-resistance-rated assemblies in concealed locations frequently require Level 1 to confirm that joints are taped.

−

−### **Level 2:** Tape embedded and covered with a skim coat of compound, fastener heads covered once. {note}

−- Used under tile and where surface appearance is not a consideration — garages, mechanical rooms, warehouse space.

−- Not suitable for paint.

−

−### **Level 3:** Tape embedded, two coats of compound on joints and angles, one coat on fastener heads, accessories coated. {note}

−- Sanded smooth.

−- Suitable for heavy or medium-texture spray finishes.

−- Not suitable for flat paint or light texture.

−

−### **Level 4:** Tape embedded, three coats on joints and angles, two coats on fasteners, accessories coated. {note}

−- Sanded smooth.

−- Suitable for flat or low-sheen paints, light textures, and most commercial finishes.

−- This is the standard finish level for commercial office, retail, and institutional applications.

−

−### **Level 5:** All surfaces receive a skim coat of joint compound or a proprietary compound over the entire board face after Level 4 preparation. {note}

−- The skim coat fills surface texture differences between the compound-covered areas and the raw board face, producing a uniform surface.

−- Required for gloss or semi-gloss paints, critical lighting environments, and high-end residential or hospitality applications.

−- Level 5 is also the correct specification for any application where the lighting angle is severe enough that board-face texture differences will be visible — sidelighting from clerestories, large windows at low angles, or track lighting.

−

−### The finish level shall be selected based on the final paint sheen.

−

−```datasheet

−label: Finish Level

−type: select

−drawing_ref: true

−options:

− - "Level 0 — no finishing"

− - "Level 1 — tape only (concealed/plenum)"

− - "Level 2 — tape + skim coat (tile base, mechanical)"

− - "Level 3 — tape + 2 coats (heavy texture surfaces)"

− - "Level 4 — tape + 3 coats (standard commercial paint grade)"

− - "Level 5 — tape + 3 coats + skim coat (gloss paint, critical lighting)"

−default: "Level 4 — tape + 3 coats (standard commercial paint grade)"

−```

−

−### When in doubt, the Architect should specify Level 5 for any space where gloss or semi-gloss paint is indicated.

−

−### For any surface that will receive wallcovering, Level 4 at minimum is required and Level 5 is recommended, because thin wallcovering printed on non-woven or paper substrates telegraphs every surface variation in the substrate.

−

−### Applying a flat paint over a Level 3 finish may be acceptable, but applying a semi-gloss or gloss paint over a Level 3 or Level 4 finish will show every fastener and joint irregularity under the reflected light. {note}

−

−## Finish at Fire-Resistance-Rated Assemblies {toc}

−

−### Where the fire-resistance design number requires a specific joint treatment — typically at minimum the equivalent of Level 1 for concealed rated assemblies — that treatment shall be applied regardless of the finish level specified for the visible face.

−

−### Both sides of a rated partition shall receive at minimum the joint treatment required by the design number, even if one side is in a concealed plenum space.

−

−## Texture Finishes {toc}

−

−```datasheet

−label: Texture Finish

−type: radio

−options:

− - "None — smooth finish"

− - "Fine orange peel spray"

− - "Medium orange peel spray"

− - "Aggregate spray (specify aggregate size)"

− - "Skip trowel"

−drawing_ref: true

−default: "None — smooth finish"

−```

−

−### Where textured finish is indicated — aggregate spray, skip trowel, orange peel, or other applied texture — it shall be applied after Level 3 or Level 4 preparation (as appropriate to the texture type) and shall be uniform in pattern, thickness, and density across the entire surface.

−

−### Texture finishes shall not be applied as a substitute for proper Level 4 preparation in applications where flat or low-sheen paint will follow, because the texture will amplify rather than hide joint and fastener irregularities.

−

−# Installation {toc}

−

−## Delivery, Storage, and Handling {toc}

−

−### Gypsum board shall be delivered to the project in the manufacturer's original packaging with all labels and markings intact.

−

−### Board shall be stored flat, on a clean, level surface, and protected from moisture.

−

−### Board shall be stored indoors in a dry, climate-controlled environment after the building is enclosed; temporary outdoor storage shall be avoided, and any board that becomes wetted shall be inspected before installation and rejected if the face paper is delaminated or the core is soft.

−

−### Steel framing shall be stored off the ground and protected from water that would cause rust.

−

−### Light surface oxidation of zinc-coated framing does not impair performance, but heavy rust that pits the metal or reduces the base metal thickness below the ASTM C645 minimum shall cause rejection.

−

−### Board stacked flat on an uneven surface will conform to the irregularity and be permanently bowed, and board stored on edge for extended periods will sag at the center. {note}

−

−## Board Application — General {toc}

−

−### Board shall be applied in conformance with ASTM C840, GA-216, and the applicable fire-resistance design number.

−

−### All framing members shall be plumb, straight, and at the correct spacing before board is applied, and studs that are twisted, bowed, or misaligned shall be corrected before boarding.

−

−### Board shall be applied with the long dimension perpendicular to framing members (horizontal on walls) wherever practical.

−

−### Where vertical application is required or where building height exceeds available board lengths, joints shall be staggered from one layer to the next and from one side of the partition to the other in rated assemblies.

−

−### Board shall be cut with a sharp utility knife scored and snapped, or with a saw where cut edges will be visible, and cut edges shall be smooth and square.

−

−### Board shall be installed with a maximum gap of 1/4 inch at joints and at perimeter conditions for non-rated assemblies; fire-resistance design numbers may impose tighter joint tolerances that shall be met.

−

−### Horizontal application on walls places tapered edges at the horizontal joints where they are easiest to finish and limits the number of butt-end joints. {note}

−

−## Fastening {toc}

−

−```datasheet

−label: Fastener Type

−type: radio

−options:

− - "Self-drilling bugle-head screws (steel framing)"

− - "Self-drilling pan-head screws (for base layer in multi-layer assemblies)"

− - "Per design number"

−drawing_ref: true

−default: "Self-drilling bugle-head screws (steel framing)"

−```

−

−```datasheet

−label: Fastener Spacing — Single-Layer Walls

−type: select

−unit: in o.c.

−options:

− - "8 in o.c. at field, 8 in at edges"

− - "12 in o.c. at field, 8 in at edges"

− - "16 in o.c. at field, 12 in at edges"

− - "Per design number"

−drawing_ref: true

−default: "12 in o.c. at field, 8 in at edges"

−```

−

−```datasheet

−label: Fastener Spacing — Single-Layer Ceilings

−type: select

−unit: in o.c.

−options:

− - "7 in o.c. nailed / 12 in o.c. screwed"

− - "Per design number"

−drawing_ref: true

−default: "7 in o.c. nailed / 12 in o.c. screwed"

−```

−

−### Fasteners shall be self-drilling, self-tapping bugle-head screws of the type and length required by ASTM C840 and by the applicable design number.

−

−### Fastener length shall be selected to provide a minimum of 5/8-inch engagement into steel framing and to avoid protruding through the framing.

−

−### Fasteners shall be driven with a screw gun set to the correct depth so that the fastener head is slightly below the board surface — creating a small dimple — without breaking the face paper.

−

−### Fasteners shall be installed beginning from the center of each board and progressing toward the edges, so that the board is pulled into contact with the framing uniformly.

−

−### Fasteners at edges shall be placed a minimum of 3/8 inch from the board edge to avoid crumbling the core.

−

−### Fasteners driven too deep break the paper and lose holding power, and fasteners left proud of the surface create ridges that telegraph through the finished joint. {note}

−

−## Multi-Layer Assembly Installation {toc}

−

−### In multi-layer assemblies — whether for fire resistance, enhanced acoustic performance, or impact resistance — the base layer shall be fully installed and fastened before the face layer is applied.

−

−### Face-layer boards shall be offset from base-layer joints both horizontally and vertically by a minimum of one stud space.

−

−### In rated assemblies, the face-layer fastener pattern shall be precisely as specified in the design number, because the face layer is the fire-exposed layer and its fastening is part of the tested configuration.

−

−### Adhesive lamination between layers may be used in specific applications to reduce fastener count in face layers and to improve rigidity.

−

−### Adhesive application shall conform to the adhesive manufacturer's instructions and to the applicable assembly design.

−

−### Adhesive alone shall not be used to attach face layers in fire-resistance-rated assemblies unless the design number specifically includes and describes the adhesive application.

−

−## Ceiling System Installation {toc}

−

−```datasheet

−label: Ceiling System Type

−type: radio

−options:

− - "Direct-attached to furring channels on framing"

− - "Suspended — hanger wire and grid system"

− - "Direct to structure (concrete deck)"

−drawing_ref: true

−default: "Direct-attached to furring channels on framing"

−```

−

−### Direct-attached ceiling systems shall have gypsum board applied to furring channels or hat channels at the spacing required by the design number and by ASTM C840.

−

−### Suspended ceiling systems shall be designed and installed with a hanger wire grid in accordance with ASTM C754.

−

−### Maximum hanger spacing is 4 feet on center perpendicular to carrying channels, and carrying channel maximum span is 4 feet between hangers.

−

−### Main runners (carrying channels) shall be spaced at 4 feet on center maximum.

−

−### Cross channels (furring channels) shall be spaced at 24 inches on center maximum for 1/2-inch board and 16 inches on center maximum for thinner board.

−

−## Ceiling Load Limits {toc}

−

−### The weight of gypsum board, insulation, mechanical items, light fixtures, and other finishes shall not exceed the carrying capacity of the framing or furring system.

−

−### Additional ceiling elements shall be supported from structural framing or independent hangers, not from the gypsum board framing, unless the ceiling assembly has been specifically designed for combined loads by a structural engineer.

−

−### Heavy items attached to gypsum board walls and ceilings — cabinetry, heavy equipment, signage — shall be attached through the gypsum board to the steel framing or to blocking provided behind the board, not to the board itself.

−

−### Gypsum board alone weighs approximately 2.2 pounds per square foot for 1/2-inch board and 2.7 pounds per square foot for 5/8-inch board, and it has very limited load capacity in fastener withdrawal perpendicular to the face. {note}

−

−# Control Joints {toc}

−

−## When Control Joints Are Required {toc}

−

−### Control joints shall be installed at the conditions below, consistent with ASTM C840 and GA-216.

−

−```datasheet

−label: Maximum Partition Length Without Control Joint

−type: range

−unit: ft

−options:

− min: 20

− max: 30

− step: 5

−default: 30

−```

−

−```datasheet

−label: Maximum Ceiling Area Between Control Joints (with perimeter relief)

−type: range

−unit: sq ft

−options:

− min: 900

− max: 2500

− step: 500

−default: 2400

−```

−

−### In walls and partitions, control joints shall be installed where the partition runs in an uninterrupted straight plane exceeding 30 linear feet without a change in plane or an opening, where the partition traverses a structural construction joint — expansion joint, seismic joint, or building expansion joint — in the base building structure, at changes in framing direction, and at locations shown on the drawings.

−

−### In ceilings with perimeter relief (floating perimeter), control joints shall be installed where linear dimensions between control joints exceed 50 feet in any direction, or where the total area bounded by control joints exceeds 2,500 square feet.

−

−### In ceilings without perimeter relief (gypsum board fixed at perimeter), control joints shall be installed where linear dimensions between control joints exceed 30 feet in any direction, or where the total area bounded by control joints exceeds 900 square feet.

−

−## Control Joint Installation {toc}

−

−```datasheet

−label: Blocking Behind Control Joints in Rated Assemblies

−type: radio

−options:

− - "Yes — solid backing per GA-234 in all rated assemblies"

− - "No — non-rated assembly only"

−drawing_ref: true

−default: "Yes — solid backing per GA-234 in all rated assemblies"

−```

−

−### Control joints shall be set plumb (on walls) or level (on ceilings) in continuous runs.

−

−### The joint shall be held in place by two rows of fasteners in the flanges, one on each side of the spine.

−

−### The board face shall be scored along both flanges of the control joint before finishing, so that the compound feathers out to the joint properly.

−

−### Joint compound shall be feathered over the flanges but shall not be applied to the spine of the control joint.

−

−### Control joints in fire-resistance-rated assemblies shall be installed in conformance with GA-234, Control Joints for Fire-Resistance Rated Assemblies.

−

−### The blocking required by GA-234 behind control joints in rated assemblies shall extend the full height of the assembly cavity and shall be attached to the framing on both sides of the joint.

−

−### GA-234 requires solid blocking behind control joints in rated assemblies so that the fire-resistance of the assembly is not compromised by the opening created by the control joint, and a control joint installed in a rated partition without blocking will fail a fire-resistance inspection. {note}

−

−## Perimeter Relief at Ceilings {toc}

−

−### Perimeter relief — a floating ceiling edge that is not fastened to the perimeter wall — allows the ceiling to expand and contract with changes in temperature and humidity without cracking. {note}

−### When perimeter relief is provided, the gypsum board at the ceiling perimeter is not fastened to the wall framing, a control joint bead or casing bead terminates the ceiling board edge, and the joint at the wall is left as a reveal or sealed with a flexible sealant. {note}

−

−### Whether perimeter relief is provided at the ceiling perimeter shall be specified for each gypsum board assembly.

−

−```datasheet

−label: Perimeter Relief Provided at Ceiling

−type: radio

−options:

− - "Yes — floating perimeter (board not fastened to perimeter walls)"

− - "No — board fastened at perimeter"

−drawing_ref: true

−default: "Yes — floating perimeter (board not fastened to perimeter walls)"

−```

−

−### Perimeter relief increases the allowable ceiling area between control joints from 900 square feet to 2,500 square feet. {note}

−

−### In large commercial ceilings, providing perimeter relief is substantially less expensive than installing the additional control joints required without it. {note}

−

−# Warranty {toc}

−

−## Manufacturer's Warranty {toc}

−

−### Gypsum board products shall be warranted by the manufacturer against defects in materials and workmanship for a minimum period of one year from the date of delivery.

−

−### Fire-resistance-rated products shall be warranted to conform to the referenced ASTM C1396 Type X designation requirements.

−

−### Glass-mat products shall be warranted against delamination of the glass-mat facing from the core.

−

−## Installer's Warranty {toc}

−

−```datasheet

−label: Installation Warranty Period

−type: select

−options:

− - "1 year from substantial completion"

− - "2 years from substantial completion"

−default: "1 year from substantial completion"

−```

−

−### The Contractor shall warrant the gypsum board installation — including all framing, fastening, jointing, and finishing — against defective workmanship for the project warranty period.

−

−### Warranty workmanship defects include, but are not limited to, fastener popping, joint ridging, joint cracking, bead delamination, and significant surface cracking caused by inadequate control joints or improper perimeter treatment.

−

−### Normal hairline cracking at joints due to seasonal environmental cycling is not a workmanship defect when control joints have been provided at the required spacing and perimeter treatment has been correctly installed. {note}

−

−## Conditions Voiding Warranty {toc}

−

−### Both the manufacturer's and the installer's warranty are voided by subsequent exposure to water damage, by modifications made by others, by application of excessive loads not anticipated in the design, and by building movement that exceeds the designed deflection capacity of the assembly.

−

−### The Contractor shall document any conditions observed during installation that may affect the performance or durability of the gypsum board system — such as evidence of water infiltration, inadequate climate control during installation, or structural irregularities — and shall bring them to the Architect's attention before completing the work.

+---

+title: Gypsum Board Assemblies

+category: Architectural

+description: >

+ When to use: Interior gypsum board partitions, furred walls, and ceilings, and the gypsum sheathing on framed exterior walls, in commercial, institutional, multifamily, and residential buildings. Covers the gypsum panel products by exposure and duty: regular, Type X, and Type C board, sag-resistant ceiling board, mold- and moisture-resistant board, glass-mat faced board, abuse- and impact-resistant board, the wet-area backer boards that carry tile on framed walls, gypsum base for veneer plaster, shaftliner in area separation walls, and glass-mat and paper-faced gypsum sheathing. Covers the nonstructural steel studs, runners, furring, and resilient channels furnished to ASTM C645 and installed to ASTM C754, the suspended and direct-attached ceiling framing that carries gypsum board, deflection heads and partition bracing, in-wall blocking and backing for the trades that hang work on these walls, execution of fire-resistance-rated and sound-rated assemblies to their design numbers, perimeter acoustic sealant and electrical box treatment, fastening, multi-layer application, trim accessories, control joints, joint treatment, levels of finish, and textured finishes.

+ Not intended for: Load-bearing and wind-bearing cold-formed framing engineered under AISI S100 and AISI S240 (see [[sync/cold-formed-metal-framing]]); single-side-access shaft walls at elevator hoistways, exit stairs, and vertical chases (see [[sync/gypsum-shaft-wall-assemblies]]); through-penetration firestop systems and listed joint systems at the head of a partition, at its base, and at penetrations (see [[sync/firestopping]]); selection and documentation of the design number for each rated assembly (see [[sync/fire-rated-wall-and-floor-assemblies]]); sound-attenuation cavity fill (see [[sync/acoustic-insulation]]); thermal insulation in the envelope and its vapor retarder (see [[sync/building-thermal-insulation]]); field painting of the finished board (see [[sync/interior-painting]]); wall coverings (see [[sync/wall-coverings]]); tile, its setting materials, and the membranes beneath it (see [[sync/ceramic-tile]]); portland cement plaster and stucco (see [[sync/plaster-and-stucco]]); acoustical tile ceilings and their suspension grids (see [[sync/suspended-acoustical-ceilings]]); doors, frames, and hardware (see [[sync/doors-frames-and-hardware]]); factory-fabricated demountable partition systems (see [[sync/demountable-partitions]]); and spray-applied fireproofing on structure (see [[sync/fireproofing]]).

+---

+# Scope {toc}

+## Work Covered by This Standard {toc}

+### This standard governs the furnishing, framing, application, finishing, and protection of gypsum board partitions, furred walls, ceilings, soffits, and bulkheads, and of gypsum sheathing on framed exterior walls. {note}

+### A gypsum board assembly is a system rather than a product. Its fire-resistance rating, its sound transmission class, its limiting height, and its abuse resistance each depend together on the board type and thickness, the number of layers, the framing depth, thickness, and spacing, the fastener type and pattern, the cavity fill, the decoupling accessories, and the perimeter treatment, and a change to any one of those variables changes what the assembly is. {note}

+### The board itself carries no rating. Type X is a core formulation defined by the performance it delivers in a tested assembly, and the hourly rating, the sound rating, and the limiting height all belong to the assembly in which the board was tested. {note}

+### The gypsum board assemblies included in the work shall be as indicated in the datasheet.

+```datasheet

+label: Gypsum Board Assemblies in Scope

+type: checkbox

+options:

+ - "Interior partitions on nonstructural steel framing"

+ - "Interior partitions on wood framing"

+ - "Furred walls over concrete and masonry"

+ - "Fire-resistance-rated partitions and horizontal membranes"

+ - "Sound-rated partitions"

+ - "Suspended gypsum board ceilings"

+ - "Direct-attached gypsum board ceilings"

+ - "Soffits and bulkheads"

+ - "Area separation walls"

+ - "Wet-area tile backer on framed walls"

+ - "Gypsum base and veneer plaster"

+ - "Gypsum sheathing on framed exterior walls"

+```

+### Several articles of this standard apply only to assemblies selected in this field, and each such article states its own trigger. {note}

+### The partition types, their board layers, their framing, their rating, and their locations shall be as indicated on [[drawing: the partition schedule and the floor plans]].

+### The ceiling types, their board, their framing, and their extents shall be as indicated on [[drawing: the reflected ceiling plans]].

+## Work Not Covered by This Standard {toc}

+### The following are governed elsewhere and are outside this standard: {note}

+- load-bearing and wind-bearing cold-formed framing engineered under AISI S100 and AISI S240, which is governed by [[sync/cold-formed-metal-framing]]

+- wood light framing, its studs, plates, and headers, which is governed by [[sync/wood-framing]], and the miscellaneous wood blocking, nailers, and furring that are governed by [[sync/rough-carpentry]]

+- single-side-access shaft walls at elevator hoistways, exit stairs, and vertical chases, which are governed by [[sync/gypsum-shaft-wall-assemblies]]

+- through-penetration firestop systems and listed joint systems at the head of a partition, at its base, and at penetrations, which are governed by [[sync/firestopping]]

+- selection and documentation of the design number for each rated assembly, which is governed by [[sync/fire-rated-wall-and-floor-assemblies]]

+- sound-attenuation cavity fill, which is governed by [[sync/acoustic-insulation]]

+- thermal insulation in the envelope and its vapor retarder, which are governed by [[sync/building-thermal-insulation]]

+- sealant materials and their chemistry, which are governed by [[sync/joint-sealants]]

+- field painting of the finished board, which is governed by [[sync/interior-painting]], and wall coverings, which are governed by [[sync/wall-coverings]]

+- tile, its setting materials, and the membranes beneath it, which are governed by [[sync/ceramic-tile]]

+- portland cement plaster and stucco, which are governed by [[sync/plaster-and-stucco]]

+- acoustical tile ceilings and their suspension grids, which are governed by [[sync/suspended-acoustical-ceilings]]

+- doors, frames, and hardware, which are governed by [[sync/doors-frames-and-hardware]], and access doors and panels themselves, which are governed by [[sync/access-doors-and-panels]]

+- spray-applied fireproofing on structure, which is governed by [[sync/fireproofing]]

+## Coordination With Adjacent Work {toc}

+### Gypsum board closes more other trades' work than any other interior finish, and most defects found after occupancy trace to something that was missing, wrong, or displaced when the board went on. {note}

+### The Contractor shall coordinate the cavity fill of sound-rated and fire-resistance-rated partitions with [[sync/acoustic-insulation]] so that the fill is in place and inspected before the closing face is applied.

+### The Contractor shall coordinate the envelope insulation, vapor retarder, and air barrier behind furred and framed exterior walls with [[sync/building-thermal-insulation]] and [[sync/air-barriers]] before the board is applied.

+### The Contractor shall coordinate the head-of-wall joint system, the bottom-of-wall joint system, and every penetration firestop in a rated assembly with [[sync/firestopping]] before the assembly is closed.

+### The Contractor shall coordinate frame anchorage, jamb reinforcement, and wall build sequence with [[sync/doors-frames-and-hardware]] before frames are delivered.

+### The Contractor shall coordinate the framing, panel installation, and finishing of access panel openings with [[sync/access-doors-and-panels]].

+### The Contractor shall coordinate the finish level of each surface with [[sync/interior-painting]] and [[sync/wall-coverings]] against the room finish schedule before joint treatment begins.

+### The Contractor shall coordinate the backer board, its framing, and its joint treatment at tiled walls with [[sync/ceramic-tile]].

+### The Contractor shall coordinate the gypsum board soffits and bulkheads that bound an acoustical ceiling field with [[sync/suspended-acoustical-ceilings]].

+### The Contractor shall coordinate the interface between an ordinary partition and a shaft wall, including the corner framing and the face-layer continuity, with [[sync/gypsum-shaft-wall-assemblies]].

+### The Contractor shall coordinate the header and hard ceiling above an operable partition with [[sync/operable-partitions]] so that the track support is framed before the ceiling is closed.

+### The Contractor shall coordinate recessed shade pockets and their framing with [[sync/window-treatments]].

+### The Contractor shall coordinate the rated openings for fire-rated glazing with [[sync/fire-rated-glazing]] so that the framing and substrate at the opening match the listed assembly.

+# Referenced Standards {toc}

+## Materials, framing, application, and finishing shall comply with the latest adopted edition of each of the following unless a specific edition is cited.

+## Where referenced standards conflict, the more stringent requirement shall govern unless the Architect of Record directs otherwise in writing.

+| Standard | Title |

+|----------|-------|

+| ASTM C1396/C1396M | Gypsum Board |

+| ASTM C1177/C1177M | Glass Mat Gypsum Substrate for Use as Sheathing |

+| ASTM C1178/C1178M | Coated Glass Mat Water-Resistant Gypsum Backing Panel |

+| ASTM C1658/C1658M | Glass Mat Gypsum Panels |

+| ASTM C1629/C1629M | Abuse-Resistant Nonstructural Gypsum Panel Products and Fiber-Reinforced Cement Panels |

+| ASTM C1278/C1278M | Fiber-Reinforced Gypsum Panel |

+| ASTM C1288 | Discrete Non-Asbestos Fiber-Cement Interior Substrate Sheets |

+| ASTM C1325 | Fiber-Mat Reinforced Cementitious Backer Units |

+| ASTM C1264 | Sampling, Inspection, Rejection, Certification, Packaging, Marking, Shipping, Handling, and Storage of Gypsum Panel Products |

+| ASTM C473 | Physical Testing of Gypsum Panel Products |

+| ASTM D3273 | Resistance to Growth of Mold on the Surface of Interior Coatings in an Environmental Chamber |

+| ASTM C645 | Nonstructural Steel Framing Members |

+| ASTM C754 | Installation of Steel Framing Members to Receive Screw-Attached Gypsum Panel Products |

+| AISI S220 | North American Standard for Cold-Formed Steel Framing, Nonstructural Members |

+| ICC-ES AC86 | Acceptance Criteria for Cold-Formed Steel Framing Members, Interior Nonload-Bearing Wall Construction |

+| ASTM A653/A653M | Steel Sheet, Zinc-Coated (Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed) by the Hot-Dip Process |

+| ASTM C635/C635M | Manufacture, Performance, and Testing of Metal Suspension Systems for Acoustical Tile and Lay-in Panel Ceilings |

+| ASTM C636/C636M | Installation of Metal Ceiling Suspension Systems for Acoustical Tile and Lay-in Panels |

+| ASTM C840 | Application and Finishing of Gypsum Board |

+| ASTM C1002 | Steel Self-Piercing Tapping Screws for Application of Gypsum Panel Products or Metal Plaster Bases to Wood Studs or Steel Studs |

+| ASTM C954 | Steel Drill Screws for the Application of Gypsum Panel Products or Metal Plaster Bases to Steel Studs from 0.033 in. to 0.112 in. in Thickness |

+| ASTM C514 | Nails for the Application of Gypsum Board |

+| ASTM C557 | Adhesives for Fastening Gypsum Wallboard to Wood Framing |

+| ASTM C475/C475M | Joint Compound and Joint Tape for Finishing Gypsum Board |

+| ASTM C1047 | Accessories for Gypsum Wallboard and Gypsum Veneer Base |

+| ASTM C587 | Gypsum Veneer Plaster |

+| ASTM C843 | Application of Gypsum Veneer Plaster |

+| ASTM C919 | Use of Sealants in Acoustical Applications |

+| ASTM E119 | Fire Tests of Building Construction and Materials |

+| UL 263 | Fire Tests of Building Construction and Materials |

+| ASTM E84 | Surface Burning Characteristics of Building Materials |

+| ASTM E136 | Behavior of Materials in a Vertical Tube Furnace at 750°C |

+| ASTM E90 | Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements |

+| ASTM E413 | Classification for Rating Sound Insulation |

+| ASTM E336 | Measurement of Airborne Sound Attenuation Between Rooms in Buildings |

+| GA-216 | Application and Finishing of Gypsum Panel Products |

+| GA-214 | Recommended Levels of Finish for Gypsum Board, Glass Mat and Fiber-Reinforced Gypsum Panels |

+| GA-234 | Control Joints for Fire-Resistance-Rated Systems |

+| GA-238 | Guidelines for Prevention of Mold Growth on Gypsum Board |

+| GA-253 | Application of Gypsum Sheathing |

+| GA-600 | Fire Resistance and Sound Control Design Manual |

+| GA-620 | Gypsum Area Separation Walls |

+| UL Fire Resistance Directory | Fire-Resistance-Rated Systems and Products |

+| ASCE/SEI 7 | Minimum Design Loads and Associated Criteria for Buildings and Other Structures (Chapter 13, Seismic Design Requirements for Nonstructural Components) |

+| IBC | International Building Code (Chapter 7, Fire and Smoke Protection Features; Chapter 25, Gypsum Board, Gypsum Panel Products and Plaster; Section 1607, Live Loads; Section 2603, Foam Plastic Insulation) |

+## GA-216 is the application document the International Building Code adopts by reference for gypsum board, so its provisions are code obligations wherever the IBC is in force, and ASTM C840 covers the same ground as a consensus standard; where the two differ on a detail this standard cites the one that governs that detail. {note}

+# Submittals {toc}

+## Action Submittals {toc}

+### The Contractor shall submit the following for review before gypsum board products or framing are procured:

+- Product data for each gypsum panel product, stating the product standard, the type designation, the thickness, the edge profile, the facing, the core treatment, the surface burning classification, and the mold resistance score where the product is furnished as mold resistant

+- Product data for studs, runners, furring channels, resilient channels, sound isolation clips, deflection track, ceiling suspension members, and hangers, stating the member designation, the base steel thickness in mils, the yield strength, the metallic coating, and the evaluation report where a member is qualified by test rather than by thickness

+- Product data for screws, nails, adhesives, joint compound, joint tape, trim accessories, control joints, acoustic sealant, and putty pads

+- A schedule listing every fire-resistance-rated assembly, the design number cited for it, and the board, framing, fastener, and cavity fill proposed to build it

+- A schedule listing every sound-rated assembly, the sound transmission class required, the tested assembly cited for it, and the decoupling accessories proposed to build it

+- Limiting height tables for the studs proposed, marked to show the tallest partition of each type on the project against the deflection limit selected

+- Shop drawings for suspended ceiling framing, showing hanger locations, carrying channel and furring spacing, bracing, perimeter conditions, and the framing at fixtures, air devices, and access panels

+- A blocking and backing schedule listing every wall-mounted item that requires backing, its location, its mounting height, and the backing material and size proposed

+- Samples of each trim accessory and control joint, and a 12 in. by 12 in. sample of each textured finish

+```datasheet

+label: Action Submittals Required

+type: checkbox

+options:

+ - "Product data for gypsum panel products"

+ - "Product data for framing, furring, and suspension members"

+ - "Product data for fasteners, compound, tape, accessories, and sealants"

+ - "Fire-resistance-rated assembly schedule"

+ - "Sound-rated assembly schedule"

+ - "Limiting height tables marked to the project"

+ - "Shop drawings for suspended ceiling framing"

+ - "Blocking and backing schedule"

+ - "Samples of accessories and textured finishes"

+default:

+ - "Product data for gypsum panel products"

+ - "Product data for framing, furring, and suspension members"

+ - "Product data for fasteners, compound, tape, accessories, and sealants"

+ - "Fire-resistance-rated assembly schedule"

+ - "Blocking and backing schedule"

+```

+### Installation of any assembly shall not begin until the submittals covering its products have been reviewed and returned.

+### The Contractor shall submit a written request before furnishing a board type, thickness, framing member, fastener, or accessory that differs from the reviewed submittal, and the request shall identify each rated or sound-rated assembly the change affects.

+## Informational Submittals {toc}

+### The Contractor shall submit the following before the first assembly is closed:

+- Evaluation reports for studs qualified under AISI S220 and ICC-ES AC86 at a base steel thickness below the ASTM C645 minimum

+- Documentation of the installer's experience meeting the qualification stated in this standard

+- Evidence that each product furnished as noncombustible, mold resistant, or abuse resistant carries the classification claimed for it

+```datasheet

+label: Informational Submittals Required

+type: checkbox

+options:

+ - "Evaluation reports for equivalent-performance studs"

+ - "Installer experience documentation"

+ - "Product classification evidence"

+default:

+ - "Installer experience documentation"

+ - "Product classification evidence"

+```

+## Closeout Submittals {toc}

+### The Contractor shall submit the following before the gypsum board work is accepted:

+- Inspection records for each rated and sound-rated assembly inspected before concealment, identifying the date, the inspecting party, the assemblies inspected, and the disposition of any deficiency

+- A record of every substitution to a design number accepted in writing during construction, with the revised design number or the engineering judgment that supports it

+- Warranty documents for each product that carries a written manufacturer warranty

+```datasheet

+label: Closeout Submittals Required

+type: checkbox

+options:

+ - "Inspection records before concealment"

+ - "Record of accepted design number substitutions"

+ - "Manufacturer warranty documents"

+default:

+ - "Inspection records before concealment"

+ - "Record of accepted design number substitutions"

+```

+# Quality Assurance {toc}

+## Installer Qualifications {toc}

+### Gypsum board and its framing shall be installed by a firm experienced in the partition, ceiling, and rated assembly types required on the project.

+### The foreman for rated assemblies shall have built fire-resistance-rated gypsum board assemblies to a cited design number on not fewer than three completed projects.

+### Where the parties disagree whether an installer's experience is comparable in scope to the work of this project, the Architect of Record shall make the initial determination.

+### The skill a rated assembly requires is not in the board hanging but in reading the design number: which layer is screwed and which is laminated, which joints are staggered, where the fasteners land, and what happens at the head, and a crew that has never been held to a listing does not know which of its habits the listing forbids. {note}

+## Pre-Installation Conference {toc}

+### Before framing for gypsum board begins, the Contractor shall hold a pre-installation conference attended by the Architect of Record, the gypsum board installer, the cavity insulation installer, the firestopping installer, the electrical installer, and the trades whose work is backed by in-wall blocking.

+### The conference shall review the rated assembly schedule, the sound-rated assembly schedule, the finish level of each surface, the deflection head details, the blocking and backing schedule, the electrical box offsets in sound-rated partitions, and the sequence by which each rated and sound-rated assembly is filled, sealed, inspected, and closed.

+### The trades that follow the framing are the ones that most often defeat it, by filling a deflection gap, running back-to-back boxes in a sound-rated bay, or closing a wall before its backing is in, which is why they attend the conference rather than only the board installer. {note}

+## Mock-Ups {toc}

+### The mock-up requirement for the gypsum board work shall be as indicated in the datasheet.

+```datasheet

+label: Mock-Up Requirement

+type: radio

+options:

+ - "Not required"

+ - "One mock-up of each fire-resistance-rated and sound-rated partition type"

+ - "One mock-up of each finish level and texture in a location the Architect of Record selects"

+default: "Not required"

+```

+### A partition mock-up finds a systemic error in the layers, the fasteners, or the perimeter at one location instead of across a floor, and a finish mock-up settles what a Level 4 surface or a knockdown texture looks like under the project's lighting before the argument can start; each costs a day of one crew, and neither is worth building on a project with a single unrated partition type and flat paint throughout. {note}

+### Where a mock-up is required, the closing face shall not be applied until the framing, cavity fill, blocking, and perimeter sealant of the mock-up have been reviewed.

+### A mock-up that does not represent the cited assembly or does not pass its review shall be corrected or rebuilt at the Contractor's expense before production assemblies of that type are closed.

+### An accepted mock-up may remain as part of the work.

+## Inspection Before Concealment {toc}

+### The assemblies whose framing, cavity fill, blocking, and perimeter treatment are inspected before the closing face is applied shall be as indicated in the datasheet.

+```datasheet

+label: Assemblies Inspected Before Concealment

+type: select

+options:

+ - "Every partition and ceiling"

+ - "Fire-resistance-rated and sound-rated assemblies"

+ - "Fire-resistance-rated assemblies"

+ - "None beyond the inspections the adopted code requires"

+default: "Fire-resistance-rated and sound-rated assemblies"

+```

+### Inspecting every wall buys certainty at the cost of holding every crew for a walk before each face goes on, and inspecting only rated assemblies leaves the blocking and box offsets in ordinary partitions to the closeout survey; the rated-and-sound-rated selection is the norm because those are the assemblies whose defects cannot be seen or corrected from the finished face. {note}

+### The Contractor shall give the inspecting party not less than two working days' notice before the closing face of an assembly selected for inspection is applied.

+### The Contractor shall not apply the closing face of an assembly selected for inspection until it has been inspected and released, or until the inspecting party has waived the inspection in writing.

+### An assembly closed without a required inspection shall be reopened at the Contractor's expense to the extent the inspecting party requires.

+### Special inspection of rated assemblies, where the adopted code requires it, is performed under [[sync/special-inspections-and-testing]] and does not replace the inspection this article requires.

+# Environmental Conditions {toc}

+## Temperature During Application and Finishing {toc}

+### Gypsum board shall not be mechanically applied when the air temperature in the space is below 40°F.

+### Joint compound, adhesive, texture, and veneer plaster shall not be applied unless the air temperature in the space has been held at or above 50°F for not less than 48 hours before application and is held there continuously until the material is dry.

+### Rapid temperature change during drying shall be avoided, and temporary heat shall be distributed so that no surface is heated directly by a flame or a hot-air discharge.

+### Drying-type compound cures by evaporation and setting-type compound by hydration, and both are slowed by cold and both crack when a surface dries faster than the material beneath it; the 48-hour lead is what brings the board and framing to temperature so that the compound is not applied to a cold substrate in a warm room. {note}

+## Ventilation and Drying {toc}

+### Ventilation shall be provided to remove moisture from the space during joint treatment and until each coat is dry.

+### Where natural ventilation does not dry each coat within the manufacturer's stated time, the Contractor shall provide mechanical ventilation or dehumidification.

+### Stagnant, humid air over fresh compound produces slow, uneven drying, and the joints that dry last are the ones that blister and ridge. {note}

+## Protection From Moisture {toc}

+### Gypsum board shall not be applied in a space that is not enclosed against weather unless the product is a glass-mat sheathing or an exterior soffit board furnished for that exposure.

+### Installed board that has been wetted shall be inspected by the Contractor before finishing, and board with face paper separation, a softened core, or visible mold growth shall be removed and replaced.

+### Paper-faced gypsum board wetted after installation and dried within a day or two commonly recovers its strength, but the paper feeds mold within about two days of staying wet, and the growth begins on the concealed face where no one sees it; GA-238 is the industry guidance on which wetted board is salvageable. {note}

+# Tested Assembly Basis {toc}

+## Fire-Resistance-Rated Assemblies {toc}

+### The design number, the hourly rating, and the assembly classification of each fire-resistance-rated partition, ceiling, and horizontal membrane shall be as indicated on [[drawing: the partition schedule and the floor and ceiling assembly schedule]].

+### The design number is selected and documented under [[sync/fire-rated-wall-and-floor-assemblies]], and this standard builds the assembly the design number describes. {note}

+### Every fire-resistance-rated assembly shall be built with the board type and thickness, the number of layers, the framing depth, thickness, and spacing, the fastener type, length, and pattern, the joint treatment, the cavity fill, and the perimeter detail that the cited design number states.

+### Where a design number names a proprietary product, the Contractor shall furnish that product or a product covered by the same listing.

+### Where a field condition prevents an assembly from being built as the design number states, the Contractor shall report the condition to the Architect of Record before proceeding and shall not build a departure without written acceptance of a substitute design number or an engineering judgment obtained under [[sync/fire-rated-wall-and-floor-assemblies]].

+### The rating an assembly earns in the furnace belongs to the whole configuration tested, and a listing does not permit a project to loosen any variable it fixes; a stud spacing opened up for economy, a screw pattern shortened, or a batt omitted because the acoustic schedule did not need it each produces a wall that was never tested. {note}

+### Gypsum board resists fire by calcination. The core holds about a fifth of its weight as chemically bound water, and driving that water off consumes heat and holds the unexposed face near the boiling point until the calcination front has passed through the thickness; the rating is largely the time that takes, which is why thickness and layer count matter more than any other variable. {note}

+## Sound-Rated Assemblies {toc}

+### The sound transmission class required of each sound-rated partition and floor-ceiling assembly shall be as indicated on [[drawing: the partition schedule and the floor and ceiling assembly schedule]].

+### The sources of tested sound-rated assembly data accepted on the project shall be as indicated in the datasheet.

+```datasheet

+label: Accepted Sources of Sound-Rated Assembly Data

+type: checkbox

+options:

+ - "GA-600 sound-rated designs"

+ - "Listed fire-resistance designs that carry a published sound transmission class"

+ - "ASTM E90 laboratory test reports from an independent accredited laboratory"

+ - "Manufacturer-sponsored ASTM E90 test reports from an accredited laboratory"

+default:

+ - "GA-600 sound-rated designs"

+ - "Listed fire-resistance designs that carry a published sound transmission class"

+ - "ASTM E90 laboratory test reports from an independent accredited laboratory"

+```

+### Each sound-rated assembly shall be built with the board layers, the framing, the decoupling accessories, the cavity fill, and the perimeter treatment of the tested assembly cited for it.

+### A sound transmission class is a laboratory rating measured under ASTM E90 and classified under ASTM E413 on a specimen with no flanking paths. A field measurement under ASTM E336 of the same assembly runs several points lower because the structure, the plenum, the doors, and the penetrations carry sound around it, and the adopted building code sets its field minimum for walls between dwelling units five points below the laboratory minimum for that reason. {note}

+### Raising a partition from the mid-40s to the mid-50s is done by decoupling one face on resilient channels or isolation clips, by adding a second layer of board, or by building a double or staggered stud wall, and each step costs cavity depth and floor area as well as money; above the mid-50s the flanking paths, not the partition, set the result. {note}

+### The construction of the flanking paths that limit field performance is addressed in the sound-rated construction articles of this standard, and field acoustic testing of completed assemblies is performed under [[sync/acoustic-insulation]]. {note}

+# Gypsum Panel Products {toc}

+## Product Standards and Labeling {toc}

+### Gypsum board shall conform to ASTM C1396 for the type designated.

+### Glass-mat faced interior board shall conform to ASTM C1658, glass-mat water-resistant backing board to ASTM C1178, glass-mat sheathing to ASTM C1177, and abuse-resistant and impact-resistant board to ASTM C1629 in addition to ASTM C1396.

+### Every panel shall bear the manufacturer's identification, the product standard, the type designation, and the thickness, and panels whose marking is illegible or absent shall not be installed.

+### Sampling, inspection, and rejection of gypsum panel products shall follow ASTM C1264.

+### The gypsum core of every panel product under this standard is noncombustible as tested under ASTM E136, and a paper-faced panel earns a Class A surface burning classification under ASTM E84; a panel's facing, not its core, is what a surface burning or mold test is measuring. {note}

+## Board Type at Non-Rated Assemblies {toc}

+### Type X board is required wherever a design number calls for it, and the decision this field records is what goes on the partitions and ceilings that carry no rating. {note}

+### The board type at non-rated partitions and ceilings shall be as indicated in the datasheet.

+```datasheet

+label: Board Type at Non-Rated Assemblies

+type: radio

+options:

+ - "Type X board throughout, at rated and non-rated assemblies alike"

+ - "Regular board at non-rated assemblies and Type X only where a design number requires it"

+```

+### Type X throughout removes the possibility of regular board being hung in a rated wall by a crew that has both on the floor, and 5/8 in. Type X is stiffer and more dent resistant than 1/2 in. regular board at a small premium per square foot; regular board at non-rated assemblies saves that premium and the weight, which is the norm in residential work where most walls are unrated and the framing is at 16 in. on center. {note}

+### Where the datasheet selects Type X throughout, regular board shall not be installed in any partition or ceiling.

+### Type C board is a Type X formulation with additional glass fiber and a shrinkage-compensating additive that keeps the core intact and in place longer under fire exposure, so that certain listings achieve a rating at fewer layers or a thinner section than Type X allows; it is furnished only where the design number names it, and Type X is not a substitute for it. {note}

+### Where a design number names Type C board, Type X board shall not be substituted for it.

+## Wall Board Thickness {toc}

+### The thickness of the board on partitions and furred walls, where a design number does not fix it, shall be as indicated in the datasheet.

+```datasheet

+label: Wall Board Thickness

+type: range

+unit: in.

+options:

+ min: 0.25

+ max: 1

+ setpoints: [0.25, 0.375, 0.5, 0.625, 0.75, 1]

+default: 0.625

+```

+### The 5/8 in. thickness is the commercial norm because it is the thickness in which Type X is listed for one-hour assemblies, it spans framing at 24 in. on center without sag or fastener telegraphing, and it takes a dent that 1/2 in. board does not; 1/2 in. board is the norm in residential work on 16 in. framing, 1/4 in. and 3/8 in. board are furnished for curved surfaces and for laminating over an existing surface, and 3/4 in. and 1 in. panels are the abuse-resistant and shaftliner products that a listing or a duty rating calls for. {note}

+### Where a design number fixes the board thickness, the design number governs.

+## Ceiling Board {toc}

+### A ceiling carries the board on its weak axis, and board that is adequate on a wall sags between supports on a ceiling, especially once a wet texture or a heavy paint has loaded it; sag-resistant ceiling board is a 1/2 in. product formulated to span 24 in. framing without that deflection. {note}

+### The board type on ceilings, where a design number does not fix it, shall be as indicated in the datasheet.

+```datasheet

+label: Ceiling Board Type

+type: select

+options:

+ - "Sag-resistant ceiling board"

+ - "Regular gypsum board"

+ - "Type X gypsum board"

+ - "Type C gypsum board"

+ - "Glass-mat faced gypsum board"

+```

+### Sag-resistant ceiling board delivers a flat 1/2 in. ceiling on 24 in. framing at the lowest weight, Type X is required by every rated horizontal membrane and is the choice where the ceiling board is also the wall board, regular board serves ceilings on 16 in. framing that receive no texture, Type C appears only where a design number calls for it, and glass-mat faced board is the product for exterior soffits and for ceilings in humid rooms. {note}

+### The thickness of the board on ceilings, where a design number does not fix it, shall be as indicated in the datasheet.

+```datasheet

+label: Ceiling Board Thickness

+type: range

+unit: in.

+options:

+ min: 0.375

+ max: 0.625

+ setpoints: [0.375, 0.5, 0.625]

+```

+### Regular 1/2 in. board applied perpendicular to framing spans 24 in. on a ceiling only where no water-based texture will follow, and 16 in. where one will; 5/8 in. board and sag-resistant 1/2 in. board span 24 in. under either finish. {note}

+### Regular 1/2 in. board shall not be applied to ceiling framing spaced wider than 16 in. on center where a water-based texture or a spray-applied finish will follow.

+## Edge Profile {toc}

+### The edge profile of the board shall be as indicated in the datasheet.

+```datasheet

+label: Board Edge Profile

+type: radio

+options:

+ - "Tapered edge"

+ - "Square edge"

+ - "Tapered edge with rounded corner"

+default: "Tapered edge"

+```

+### A tapered edge recesses the tape and compound below the face so that a flat joint can be finished flush, which is why it is the norm for every surface that will be finished; a square edge is furnished where the board is a base layer, a tile backer, or a sheathing that will never see compound, and the rounded-corner taper is a variant that reduces edge crushing during handling at the same finishing behavior. {note}

+### Butt ends of the board are always square, and the joint between two butt ends is finished with a wider feather than a tapered joint or is back-blocked to form a recess. {note}

+## Board at Intermittently Damp Locations {toc}

+### The board at toilet rooms, locker rooms, janitor closets, kitchens, and other rooms with intermittent moisture and elevated humidity, where the surface will not be tiled, shall be as indicated in the datasheet.

+```datasheet

+label: Board at Intermittently Damp Locations

+type: select

+options:

+ - "Mold- and moisture-resistant paper-faced gypsum board"

+ - "Glass-mat faced gypsum board"

+ - "Regular or Type X gypsum board without moisture treatment"

+```

+### Mold- and moisture-resistant paper-faced board carries a treated core and a treated face that score 10 under ASTM D3273, at a small premium over regular board and with the same finishing behavior; glass-mat faced board replaces the paper with an inorganic mat that gives mold nothing to feed on and tolerates repeated wetting, at a higher premium and with a face that takes compound differently; untreated board is the choice where the room is conditioned, the moisture is occasional, and the finish is a washable paint. {note}

+### The rooms and surfaces that receive the board selected in this field shall be as indicated on [[drawing: the room finish schedule]].

+### Board furnished as mold resistant shall score 10 when tested under ASTM D3273.

+### No gypsum board of any facing shall be installed where the surface will be continuously wet or in continuous high humidity, including steam rooms, saunas, gang showers, and indoor pool enclosures, and the substrate at those locations shall be as indicated on [[drawing: the room finish schedule]].

+## Abuse- and Impact-Resistant Board {toc}

+### Requirements in this article apply where abuse-resistant or impact-resistant board is designated on the partition schedule.

+### ASTM C1629 classifies a panel in four categories, surface abrasion, indentation, soft-body impact, and hard-body impact, each at Level 1, 2, or 3 with 3 the most resistant; the products sold as abuse resistant carry a dense, fiber-reinforced core and a heavier face and reach the upper levels in abrasion and indentation, and the products sold as impact resistant add an embedded mesh that reaches Level 3 in hard-body impact. {note}

+### The enhanced-durability board furnished at designated locations shall be as indicated in the datasheet.

+```datasheet

+label: Enhanced-Durability Board at Designated Locations

+type: select

+options:

+ - "Abuse-resistant gypsum board"

+ - "Impact-resistant gypsum board"

+ - "Impact-resistant gypsum board with embedded reinforcing mesh"

+ - "Fiber-reinforced gypsum panel conforming to ASTM C1278"

+```

+### Abuse-resistant board resists the scuffs, gouges, and dents of carts and furniture in a corridor at a modest premium and is finished like standard board; impact-resistant board resists the through-penetration of a hard object, which is what a gymnasium, a psychiatric unit, or a detention corridor needs, at a higher premium and with a face that is harder to cut and fasten; the mesh-reinforced product holds together after the core is broken, and a fiber-reinforced gypsum panel is a homogeneous product without a face paper that resists all four categories and is the heaviest of the group. {note}

+### The minimum hard-body impact classification of the board furnished shall be as indicated in the datasheet.

+```datasheet

+label: Minimum Hard-Body Impact Classification per ASTM C1629

+type: range

+unit: level

+options:

+ min: 1

+ max: 3

+ setpoints: [1, 2, 3]

+```

+### The locations that receive enhanced-durability board, and the height to which it extends, shall be as indicated on [[drawing: the partition schedule and the interior elevations]].

+### The resistance of a wall to impact is a property of the assembly, and board classified under ASTM C1629 delivers its rating only on framing at the spacing and thickness the manufacturer's classification test used. {note}

+### Enhanced-durability board shall be applied to framing at not wider than the spacing, and not thinner than the thickness, that the manufacturer's ASTM C1629 classification was tested on.

+## Wet-Area Tile Backer Board {toc}

+### Requirements in this article apply where wet-area tile backer is selected in the datasheet field for the assemblies in scope.

+### The backer board behind tile at tubs, showers, and other wet walls on framed construction shall be as indicated in the datasheet.

+```datasheet

+label: Wet-Area Tile Backer Board

+type: select

+options:

+ - "Glass-mat water-resistant gypsum backing board conforming to ASTM C1178"

+ - "Fiber-mat reinforced cementitious backer unit conforming to ASTM C1325"

+ - "Fiber-cement backer sheet conforming to ASTM C1288"

+ - "Fiber-reinforced gypsum backer conforming to ASTM C1278"

+```

+### A glass-mat gypsum backer is cut and fastened like gypsum board, weighs the least, and is the choice where the crew hanging the walls also hangs the backer; a cementitious backer unit is unaffected by water even at a failed membrane and is the choice where the tile is heavy or the wall will be wet daily, at twice the weight and with a cutting and fastening method of its own; a fiber-cement sheet sits between the two in weight and cost, and a fiber-reinforced gypsum backer has no facing to delaminate but is the least common of the four. {note}

+### The wet walls that receive backer board, and the height to which it extends, shall be as indicated on [[drawing: the room finish schedule and the interior elevations]].

+### Paper-faced gypsum board, including moisture-resistant paper-faced board, shall not be installed as the substrate for tile at tubs, showers, or other surfaces that will be wetted in service.

+### Backer board shall be installed with the fastener type and spacing, the joint tape, and the joint treatment the backer manufacturer publishes for tile, and the joint compound used at painted board shall not be used at backer joints that will be tiled.

+### Backer board on ceilings shall be applied to framing at not wider than the spacing the backer manufacturer publishes for ceiling application.

+### The waterproofing membrane, the setting mortar, and the tile over the backer are furnished under [[sync/ceramic-tile]]. {note}

+## Gypsum Base and Veneer Plaster {toc}

+### Requirements in this article apply where gypsum base and veneer plaster are selected in the datasheet field for the assemblies in scope.

+### Veneer plaster is a thin, hard, hand-applied gypsum finish over a gypsum base panel with a face paper made to bond it, and it gives a monolithic surface that is harder and more abrasion resistant than finished gypsum board at about the same installed cost as a Level 5 finish; the base panel is hung and fastened like gypsum board, so the assembly is specified here rather than with lath and plaster. {note}

+### The veneer plaster system shall be as indicated in the datasheet.

+```datasheet

+label: Veneer Plaster System

+type: radio

+options:

+ - "One-coat veneer plaster"

+ - "Two-coat veneer plaster with a basecoat and a finish coat"

+ - "Gypsum base finished as gypsum board without veneer plaster"

+```

+### A one-coat system is a single finish coat of about 1/16 in. troweled over the base and reaches a smooth or textured finish in one pass, at the lowest cost and with the least tolerance for an uneven base; a two-coat system adds a basecoat that fills the joints and levels the surface, which doubles the labor and produces a harder, flatter wall; finishing the base as gypsum board is the fallback where the base was furnished and the veneer plaster is later dropped from the scope. {note}

+### Gypsum base for veneer plaster shall conform to ASTM C1396.

+### Veneer plaster shall conform to ASTM C587 and shall be applied under ASTM C843.

+### Joints in gypsum base shall be reinforced with the glass fiber mesh tape and the joint treatment ASTM C843 requires, and paper tape and drying-type joint compound shall not be used under veneer plaster.

+### The face paper of gypsum base loses its bond to veneer plaster after prolonged exposure to sunlight, and base that has faded before plastering has to be treated with a bonding agent or replaced. {note}

+### Gypsum base whose face paper has faded from light exposure shall be treated with the bonding agent the plaster manufacturer specifies before veneer plaster is applied.

+# Gypsum Sheathing {toc}

+## Sheathing Product {toc}

+### Requirements in this article apply where gypsum sheathing is selected in the datasheet field for the assemblies in scope.

+### Gypsum sheathing is the noncombustible substrate on a framed exterior wall that carries the water-resistive barrier and, where the wall is rated, contributes to the listed assembly; the wall's cavity insulation, the air and water barrier over the sheathing, and the cladding attachment through it are each governed by their own standards. {note}

+### The gypsum sheathing product shall be as indicated in the datasheet.

+```datasheet

+label: Gypsum Sheathing Product

+type: radio

+options:

+ - "Glass-mat gypsum sheathing conforming to ASTM C1177"

+ - "Paper-faced gypsum sheathing conforming to ASTM C1396"

+default: "Glass-mat gypsum sheathing conforming to ASTM C1177"

+```

+### Glass-mat sheathing is the norm because its inorganic facing tolerates months of weather exposure before the cladding goes on and does not feed mold, while paper-faced sheathing, even with a water-resistant core, loses its face in weeks of exposure and remains a product for walls that are clad within days of sheathing. {note}

+### The thickness of the gypsum sheathing shall be as indicated in the datasheet.

+```datasheet

+label: Gypsum Sheathing Thickness

+type: range

+unit: in.

+drawing_ref: "the exterior wall types"

+options:

+ min: 0.5

+ max: 0.625

+ setpoints: [0.5, 0.625]

+default: deferred

+```

+### Sheathing thickness follows the wall type, because a rated exterior wall calls for 5/8 in. Type X sheathing as part of its listing and an unrated wall commonly carries 1/2 in., and the exterior wall types carry that answer per wall. {note}

+## Sheathing Application and Exposure {toc}

+### Gypsum sheathing shall be applied under GA-253 and the sheathing manufacturer's published instructions.

+### Sheathing shall be fastened with corrosion-resistant screws of the type and at the spacing the manufacturer publishes for the framing material and thickness, and where the sheathing is part of a listed assembly, at the spacing the design number states.

+### Sheathing shall not remain exposed to weather beyond the period the manufacturer publishes for the product before the water-resistive barrier is applied over it.

+### Sheathing that has been exposed beyond the published period, or that shows a softened core, delaminated facing, or mold growth, shall be removed and replaced before the barrier is applied.

+### The water-resistive barrier and the air barrier over the sheathing are furnished under [[sync/air-barriers]], and the flashing at openings through the sheathing under the standard that governs the cladding. {note}

+### Where gypsum sheathing is the substrate for an exterior insulation and finish system, its thickness, fastening, and joint treatment shall additionally satisfy [[sync/exterior-insulation-and-finish-systems]].

+# Nonstructural Steel Framing {toc}

+## Framing Standards and Loads {toc}

+### Nonstructural steel studs, runners, furring channels, and resilient channels shall conform to ASTM C645 and shall be installed under ASTM C754.

+### Nonstructural framing carries the weight of the board and its finishes and resists the lateral load the adopted building code assigns to interior partitions, which IBC Section 1607 sets at 5 psf, and it is selected from the manufacturer's limiting height tables rather than designed member by member. {note}

+### Framing that carries gravity load from the structure, resists wind pressure on an exterior wall, or forms part of a shear wall is structural and is furnished under [[sync/cold-formed-metal-framing]] regardless of what it supports.

+### Nonstructural framing shall not be used to support mechanical equipment, plumbing fixtures, casework, or any other item whose weight is not accounted for in the limiting height table used, unless the framing is reinforced under a detail the Architect of Record accepts.

+### Each stud, runner, and channel shall carry the manufacturer's legible identification of the member designation, the base steel thickness, and the yield strength.

+## Stud Thickness Basis {toc}

+### ASTM C645 sets a minimum base steel thickness of 18 mil for a nonstructural stud. Equivalent-performance studs, sold as EQ studs, are formed from thinner, higher-strength steel with a stiffened profile and are qualified by test under AISI S220 and ICC-ES AC86 to the limiting height of the member they replace; they dominate the market, and a specification that names 18 mil without saying whether EQ studs are accepted is the source of a standing dispute on delivery. {note}

+### The basis on which nonstructural studs are accepted shall be as indicated in the datasheet.

+```datasheet

+label: Nonstructural Stud Thickness Basis

+type: radio

+options:

+ - "Minimum base steel thickness per ASTM C645 without equivalent-performance substitution"

+ - "Equivalent-performance studs qualified under AISI S220 and ICC-ES AC86 accepted at their published limiting heights"

+```

+### Where equivalent-performance studs are accepted, each such member shall be covered by a current evaluation report, and its limiting height at the deflection limit selected shall be taken from that report and not from the tables for the member it replaces.

+### Where equivalent-performance studs are accepted, screws into them shall be of the type the evaluation report and the fastener manufacturer publish for the reduced thickness.

+### Equivalent-performance studs shall not be used in a listed assembly unless the design number or the evaluation report covers their use in it.

+## Stud Web Depth {toc}

+### The web depth of nonstructural studs shall be as indicated in the datasheet.

+```datasheet

+label: Nonstructural Stud Web Depth

+type: range

+unit: in.

+drawing_ref: "the partition schedule"

+options:

+ min: 1.625

+ max: 8

+ setpoints: [1.625, 2.5, 3.625, 4, 6, 8]

+default: deferred

+```

+### Stud depth is set per partition type by the height, the plumbing and conduit the cavity has to pass, the cavity the sound rating needs, and the door frame throat, and a project with chase walls and corridor walls has several answers, which is why the partition schedule carries it. {note}

+### Where the datasheet records a depth for the work and the partition schedule states a different depth for a partition type, the partition schedule governs for that type.

+## Stud Base Steel Thickness {toc}

+### The base steel thickness of the studs in each partition type shall be as indicated in the datasheet.

+```datasheet

+label: Nonstructural Stud Base Steel Thickness

+type: range

+unit: mil

+derived: "the partition height, the stud web depth and spacing, the 5 psf interior partition load, and the deflection limit selected"

+options:

+ min: 15

+ max: 54

+ setpoints: [15, 18, 30, 33, 43, 54]

+default: derived

+```

+### Stud thickness follows from the limiting height tables once the height, the depth, the spacing, the load, and the deflection limit are known, and the same inputs give the same member on every project, which is why the field is derived rather than chosen; the 15 mil setpoint is the equivalent-performance product and is selectable only where the thickness basis accepts it. {note}

+### The Contractor shall select the stud thickness for each partition type from the manufacturer's limiting height table, or from the evaluation report for an equivalent-performance stud, for the tallest partition of that type, at the spacing installed and at the deflection limit selected in this standard.

+### Where a listed assembly or a door frame anchorage detail requires a thicker stud than the limiting height table, the thicker stud governs.

+## Stud Spacing {toc}

+### The spacing of nonstructural studs shall be as indicated in the datasheet.

+```datasheet

+label: Nonstructural Stud Spacing

+type: range

+unit: in. o.c.

+options:

+ min: 8

+ max: 24

+ setpoints: [8, 12, 16, 24]

+default: 16

+```

+### Spacing at 16 in. is the norm because it is what most listings, most limiting height tables, and most tile and abuse-resistant board classifications were tested at; 24 in. spacing saves a third of the studs on a plain partition and is admissible wherever the board thickness, the height, and the listing allow it, and 12 in. or 8 in. spacing is the answer at tall partitions, heavy finishes, and shear-loaded gypsum walls. {note}

+### Where a listed assembly, a board classification, or a tile backer manufacturer requires a closer spacing than the datasheet value, the closer spacing governs for that assembly.

+### Studs shall be spaced from a common end of each wall so that board edges land on studs.

+## Partition Deflection Limit {toc}

+### The deflection limit under the interior partition load at which limiting heights are read shall be as indicated in the datasheet.

+```datasheet

+label: Partition Deflection Limit

+type: radio

+options:

+ - "L/120"

+ - "L/240"

+ - "L/360"

+default: "L/240"

+```

+### The adopted building code permits L/120 for a partition with flexible finishes and requires L/240 for one with brittle finishes, and L/240 is the norm for gypsum board because taped joints and paint crack at deflections a flexible finish tolerates; L/360 is selected where the wall carries tile, stone, or a veneer plaster, and it costs a thicker or deeper stud at every height. {note}

+### Partitions that carry tile, stone, or veneer plaster shall be framed to a deflection limit of not less than L/360 regardless of the datasheet selection.

+## Metallic Coating on Framing {toc}

+### The minimum metallic coating on nonstructural framing members shall be as indicated in the datasheet.

+```datasheet

+label: Minimum Metallic Coating on Nonstructural Framing

+type: select

+options:

+ - "G40 zinc coating conforming to ASTM A653"

+ - "G60 zinc coating conforming to ASTM A653"

+ - "G90 zinc coating conforming to ASTM A653"

+ - "Coating with corrosion resistance equivalent to G40 as ASTM C645 permits"

+default: "G40 zinc coating conforming to ASTM A653"

+```

+### G40 is the ASTM C645 minimum and the norm for framing that will spend its life in a dry, conditioned cavity; G60 and G90 buy longer life in a cavity that can wet, at a furred exterior wall or a wet room, and the equivalent-coating option admits the proprietary coatings that ASTM C645 accepts at G40 performance and that equivalent-performance studs commonly carry. {note}

+### Framing in a furred exterior wall, in a natatorium, or in a room with a floor drain shall carry not less than a G60 coating regardless of the datasheet selection.

+## Runners and Anchorage {toc}

+### Runners shall be of the same depth as the studs they receive and of not less than the stud thickness.

+### Floor runners shall be anchored to the slab at not more than 24 in. on center and within 2 in. of each end of every runner section and each side of every opening.

+### Runners at concrete shall be anchored with powder-actuated fasteners, pneumatically driven pins, or post-installed anchors whose capacity in the slab is established by a current evaluation report, and driven fasteners shall not be installed where they would strike post-tensioning tendons or embedded conduit.

+### Studs shall be set into the runners with their flanges in the same direction and shall be fastened to the runner at both flanges where the stud is at a jamb, a corner, an intersection, or the end of a wall.

+### Studs in the field of a wall are commonly left unfastened at the runner so that the board fastening squares them, which is admissible under ASTM C754 and is the practice that lets a deflection head work; studs at jambs and corners are fastened because they carry a door or a return that the board alone will not hold square. {note}

+## Head of Partition and Deflection {toc}

+### The head condition of each partition type, whether it stops at the ceiling, extends above the ceiling and is braced, or extends to the underside of the structure, shall be as indicated on [[drawing: the partition schedule]].

+### A partition that extends to the underside of the structure above shall be framed with a deflection head that lets the structure deflect without loading the studs or the board.

+### The deflection head type at partitions extending to the structure shall be as indicated in the datasheet.

+```datasheet

+label: Deflection Head Type

+type: select

+options:

+ - "Deep-leg deflection runner with the studs unattached to the runner legs"

+ - "Slotted deflection runner fastened to each stud through the slots"

+ - "Nested double runner"

+ - "Proprietary slide clip at each stud"

+ - "Fixed runner with a compressible joint and the board held clear of the structure"

+```

+### A deep-leg runner is the least expensive head and the one most listings show, and it relies on the stud being cut short and left unattached, which a crew defeats by screwing the runner to the stud; a slotted runner keeps the stud positively attached while letting it slide, at a higher cost per foot; a nested double runner and a slide clip each provide larger movement and a firmer lateral hold at a partition that is tall or heavily loaded; and a fixed runner with a compressible joint is the head at a partition where the structure above is stiff enough that the calculated deflection is within what the joint absorbs. {note}

+### The vertical movement capacity provided at the head of each full-height partition shall be as indicated in the datasheet.

+```datasheet

+label: Vertical Movement Capacity at the Head of Partition

+type: range

+unit: in.

+derived: "the calculated deflection of the structure above each partition stated on the structural general notes"

+options:

+ min: 0

+ max: 2

+ setpoints: [0, 0.5, 0.75, 1, 1.5, 2]

+default: derived

+```

+### The movement a head has to absorb is the calculated live-load deflection of the structure above, and the structural general notes state it, so the capacity follows from that number rather than from a choice made here; a capacity of zero is the fixed head at a partition that stops below a stiff slab or at the ceiling. {note}

+### Studs at a deflection head shall be cut short of the inside of the runner by not less than the movement capacity provided.

+### Board shall be held clear of the structure above at a deflection head by the same distance and shall not be fastened to the deflection runner.

+### The gap at the head of a rated partition shall be closed with the listed joint system that [[sync/firestopping]] furnishes for the movement capacity provided, and this standard shall not fill it with board, compound, or unlisted sealant.

+### The head of a rated partition is the most frequently cited deficiency in rated construction, and the defect is almost always a trade filling the movement gap with something the listing does not permit, or a stud cut long enough to bear on the runner and turn the partition into a column. {note}

+## Partition Bracing Above Ceilings {toc}

+### Partitions that stop above a suspended ceiling and do not reach the structure shall be braced laterally to the structure at not more than 48 in. on center along the partition and at each end.

+### Partitions taller than 6 ft, and partitions that a suspended ceiling is attached to, shall be laterally braced to the structure where ASCE 7 Chapter 13 requires it for [[parameter: seismic-design-category]].

+### Bracing shall be steel studs or runners, or diagonal steel strap with a stiffener, fastened to the top runner and to the structure, and shall not be fastened to a ceiling suspension system, a duct, or a pipe.

+### A partition that leans on the ceiling grid for its lateral support loads the grid with a force it was not designed for, and the grid transmits the partition's movement into every tile and fixture along it. {note}

+## Openings and Jamb Framing {toc}

+### Each side of a door opening, a borrowed light, a rated glazing frame, and an access panel shall be framed with a jamb stud of not less than the field stud thickness, fastened to the floor and head runners at both flanges.

+### Door frames in nonstructural partitions shall be anchored to jamb studs of the thickness and configuration the frame anchorage under [[sync/doors-frames-and-hardware]] requires, and jamb studs shall be doubled, boxed, or increased in thickness where that anchorage requires it.

+### A header shall be framed above each opening from a runner section cut and bent over the jamb studs, or from a stud, and cripple studs shall continue the field spacing above the header and below any sill.

+### Openings in rated partitions shall be framed as the design number and the opening protective listing state, and the board around a rated frame shall be fastened at the spacing the listing states.

+### Openings for access panels in walls and ceilings shall be framed to the panel manufacturer's rough opening, and the panel shall be installed and finished so that its frame is flush with the board and, where the panel is in a rated assembly, so that the listed panel and its framing maintain the rating.

+### Board joints shall not fall at the corner of an opening, and the board shall be cut so that a joint occurs not less than 8 in. from a jamb.

+### A joint at the corner of an opening cracks under the racking a door swing produces, which is why the board is cut around the opening in an L rather than pieced to it. {note}

+## Furring at Concrete and Masonry {toc}

+### Requirements in this article apply where furred walls are selected in the datasheet field for the assemblies in scope.

+### The furring that carries board on concrete and masonry walls shall be as indicated in the datasheet.

+```datasheet

+label: Furring at Concrete and Masonry Walls

+type: select

+options:

+ - "Hat-shaped furring channel fastened to the wall"

+ - "Z-shaped furring channel with rigid insulation between the channels"

+ - "Nonstructural studs set clear of the wall as a freestanding furred wall"

+ - "Resilient channel fastened to the wall"

+```

+### Hat channel is the least expensive furring and holds the board about 7/8 in. off the wall, which is enough to flatten a masonry wall but leaves no room for insulation or services; Z-furring is the product for a wall that receives rigid insulation between the channels and holds the board off by the insulation thickness; a freestanding stud wall clears the masonry entirely, gives a full cavity for insulation and conduit, and breaks the thermal and acoustic bridge that a channel screwed to the wall carries, at the cost of a stud wall's floor area; and resilient channel on masonry is the furring at a sound-rated wall where the mass of the masonry is to be decoupled from the board. {note}

+### Furring channels shall be fastened to concrete and masonry at not more than 24 in. on center with fasteners whose capacity in the substrate is established by a current evaluation report.

+### Furring channels shall be installed at not more than 24 in. on center for 1/2 in. and 5/8 in. board applied perpendicular to them, and at 16 in. on center for board applied parallel.

+### Where the furred wall is on the interior face of an exterior wall, the insulation and vapor retarder between the furring are furnished under [[sync/building-thermal-insulation]], and the furring shall be installed so that the insulation is continuous behind it.

+### Furring on a below-grade or exterior masonry wall shall be isolated from the masonry by the method the wall's moisture control design requires so that moisture in the wall does not reach the board.

+## Resilient Channels and Decoupling {toc}

+### The decoupling method at each sound-rated assembly, whether resilient channel, sound isolation clips with hat channel, a double stud wall, or a staggered stud wall, is fixed by the tested assembly cited for it on the partition schedule, and a method the tested assembly did not use is a different assembly. {note}

+### Resilient channels shall be single-leg channels conforming to ASTM C645, installed with the attachment flange down and the open side up unless the tested assembly shows otherwise, at not more than 24 in. on center and within 6 in. of the floor and the ceiling.

+### Board on resilient channel shall be fastened with screws of a length that engages the channel and does not reach the framing behind it.

+### Board on resilient channel shall not be fastened at any point where a stud is behind the channel.

+### Resilient channel works by letting the board float on the flexible leg of the channel, and a single screw that passes through the channel into the stud, or a channel screwed at a stud where it crosses one, ties the board back to the framing and drops the assembly by ten or more points; it is the most common cause of a sound-rated partition failing its field test. {note}

+### Where sound isolation clips are used, the clips and the hat channel they carry shall be the products the tested assembly names, at the spacing it states.

+### Base trim, casework, and fixtures at a resiliently mounted face shall not be fastened through the board into the framing behind the channel.

+## Blocking and Backing {toc}

+### Wall-mounted items are attached to what is behind the board, not to the board, and the wall closes weeks before most of them arrive; the backing has to be located from the mounting heights and anchor patterns of the items themselves, so this article is executed against the blocking and backing schedule rather than against the framing plan. {note}

+### The Contractor shall install blocking or backing behind the board at every location where a wall-mounted item is shown on [[drawing: the interior elevations and the equipment and accessory schedules]].

+### Blocking and backing shall be located from the reviewed shop drawings and mounting heights of the supported work and shall extend not less than 6 in. beyond the anchor pattern of the item in each direction.

+### The material of the in-wall backing shall be as indicated in the datasheet.

+```datasheet

+label: In-Wall Backing Material

+type: select

+options:

+ - "Flat steel backing plate screwed across the stud flanges"

+ - "Proprietary steel backing bracket or channel clipped to the studs"

+ - "Fire-retardant-treated wood blocking let into the studs"

+ - "Untreated wood blocking let into the studs"

+ - "Plywood backing screwed to the stud faces"

+```

+### A flat steel plate is the norm in steel-framed partitions because it is cut and screwed by the framing crew and does not depend on a wood product in a noncombustible building; a proprietary bracket sets faster where the backing is standardized across many rooms; fire-retardant-treated wood is admissible in a noncombustible building where the adopted code permits it in a nonbearing partition and gives a fastener the withdrawal grip that a thin plate does not; untreated wood is the choice in a combustible building; and plywood backing gives a continuous field of anchorage behind a wall that carries a run of casework or a display system. {note}

+### Where [[parameter: adopted-building-code]] limits combustible material in the partitions of the building's type of construction, wood blocking shall be fire-retardant-treated and shall be furnished under [[sync/rough-carpentry]].

+### Steel backing plates shall be of the thickness the anchorage of the supported item requires and shall be fastened to each stud flange they cross with not fewer than two screws.

+### Grab bars, handrails, and other items whose anchorage carries a code-required load shall be backed with material and fastening that develop that load, and a backing plate thinner than the anchorage of the item requires shall not be used for them.

+### Blocking and backing shall be installed and inspected before the board is applied, and a wall closed before its scheduled backing is in shall be reopened at the Contractor's expense.

+### The Contractor shall mark the location of each concealed backing on the floor or the ceiling, or record it on the as-built framing drawings, so that the installing trade can find it after the wall is finished.

+### The trades whose work depends on this backing include the wall stops and holders under [[sync/door-hardware]], the grab bars and accessories under [[sync/toilet-accessories]], the compartments under [[sync/toilet-compartments]], the crash rails and corner guards under [[sync/wall-and-corner-protection]], the dimensional signs under [[sync/signage]], the shade brackets under [[sync/window-treatments]], the markerboards under [[sync/visual-display-units]], the lockers under [[sync/metal-lockers]], and the casework, trim, and paneling under [[sync/wood-and-laminate-casework]], [[sync/architectural-wood-trim-and-paneling]], and [[sync/interior-architectural-woodwork]]. {note}

+### Recessed accessories, fire extinguisher cabinets, and recessed units shall be framed with a rough opening to the unit's published dimensions, with a jamb stud on each side and a header and sill between them.

+# Ceiling Framing {toc}

+## Ceiling Framing System {toc}

+### Requirements in this article apply where suspended or direct-attached gypsum board ceilings are selected in the datasheet field for the assemblies in scope.

+### The framing that carries gypsum board ceilings shall be as indicated in the datasheet.

+```datasheet

+label: Gypsum Board Ceiling Framing System

+type: select

+options:

+ - "Cold-rolled carrying channels and hat furring channels suspended on hanger wire under ASTM C754"

+ - "Proprietary drywall suspension grid conforming to ASTM C635 and installed under ASTM C636"

+ - "Hat furring channels attached directly to the structure or to joists"

+ - "Nonstructural steel studs or joists spanning between walls or beams"

+```

+### The channel-and-wire system is the traditional suspension, is what most rated horizontal membranes were tested on, and is built from stock members by any framing crew; a drywall grid installs faster, holds a flatter plane, and carries its own listings for rated membranes and seismic bracing, at a higher material cost; direct-attached furring is the ceiling on a wood or steel joist floor above or on a concrete deck where no plenum is needed; and studs or joists spanning wall to wall carry a soffit or a small ceiling where hangers cannot be placed. {note}

+### The ceiling framing system at a rated horizontal membrane shall be the system the design number was tested with.

+### Where the framing spans wall to wall, the members shall be selected from the manufacturer's span tables for the ceiling load at a deflection limit of L/240.

+## Suspension Members and Spacing {toc}

+### Hangers, carrying channels, furring channels, and their spacing and attachment shall comply with ASTM C754 for the board thickness and orientation installed.

+### Hangers shall be attached to the structure with an anchorage established for the hanger load, and hangers shall not be attached to ducts, pipes, conduit, or the deck flutes of a steel deck.

+### Hangers shall be plumb and shall be placed within 6 in. of the end of each carrying channel and at each side of every opening in the ceiling that interrupts a channel.

+### Where a hanger cannot be placed at the spacing required because of an obstruction, a trapeze or a supplemental carrying member shall be installed to carry the interrupted hanger load, and the hanger spacing shall not be opened up.

+### Furring channels shall be attached to carrying channels with the clips or saddle ties ASTM C754 permits and shall be lapped at splices by not less than 8 in. with the lap tied at both ends.

+### Recessed luminaires, air devices, and access panels shall be framed with supplemental furring on all sides of the opening and shall be supported independently of the board.

+## Ceiling Bracing and Perimeter {toc}

+### Suspended gypsum board ceilings shall be laterally braced to the structure where ASCE 7 Chapter 13 requires it for [[parameter: seismic-design-category]].

+### A screw-attached gypsum board ceiling on a single level that extends from wall to wall is exempt from the seismic bracing provisions of ASCE 7 for suspended ceilings, and a gypsum board ceiling with a step, a free edge, or a large opening is not; the exemption is what makes most gypsum ceilings simpler to build than an acoustical grid in the same room. {note}

+### Where the ceiling has a free edge, a change in level, or an opening larger than the furring spacing, the framing at that edge shall be braced to the structure.

+### The perimeter of a suspended ceiling shall be supported at the wall by a wall angle or a runner where the ceiling is fixed at the perimeter, or shall be held clear of the wall where perimeter relief is selected in this standard.

+## Soffits and Bulkheads {toc}

+### Soffits, bulkheads, and the vertical faces that bound an acoustical ceiling field shall be framed with nonstructural studs and runners braced to the structure at not more than 48 in. on center, or with a proprietary soffit framing system installed under its evaluation report.

+### The dimensions, profiles, and locations of soffits and bulkheads shall be as indicated on [[drawing: the reflected ceiling plans and the ceiling details]].

+### The bottom of a bulkhead that receives the edge of an acoustical ceiling shall be framed to carry the wall angle of that ceiling at the height its suspension requires, coordinated under [[sync/suspended-acoustical-ceilings]].

+### A bulkhead at a rated corridor or a rated horizontal membrane shall be built to the design number cited for the membrane, and the joint between the bulkhead and the membrane shall be closed as that design number requires.

+## Rated Horizontal Membranes {toc}

+### Requirements in this article apply where fire-resistance-rated horizontal membranes are selected in the datasheet field for the assemblies in scope.

+### A rated gypsum board ceiling is the membrane of a floor-ceiling or roof-ceiling assembly, or the horizontal enclosure of a corridor or a shaft, and it earns its rating only as part of the assembly the design number describes, including the structure above it, the cavity fill, and the openings through it. {note}

+### The board type, thickness, layers, furring spacing, fastener pattern, and joint treatment of a rated horizontal membrane shall be as the cited design number states.

+### Openings in a rated membrane for luminaires, air devices, and access panels shall be limited to the size and aggregate area the design number permits and shall be protected as it requires.

+### Where the design number requires a specific clip, channel, or grid for the membrane, that product shall be furnished and shall not be substituted.

+### A rated horizontal membrane shall not be penetrated by hangers, wires, or supports for work below it except as the design number permits.

+# Fire-Resistance-Rated Construction {toc}

+## Execution to the Design Number {toc}

+### Requirements in this article apply where fire-resistance-rated partitions and horizontal membranes are selected in the datasheet field for the assemblies in scope.

+### The base layer in a multi-layer rated assembly shall be fully fastened at the pattern the design number states before the face layer is applied, and the face layer shall be fastened or laminated as the design number states.

+### Joints in the face layer shall be offset from joints in the base layer by not less than one framing space, and joints on opposite faces of a rated partition shall be staggered so that no joint on one face is opposite a joint on the other.

+### Joints and fastener heads in a rated assembly shall be treated with tape and compound as the design number and [[parameter: adopted-building-code]] require, and a joint that will be concealed shall receive not less than the Level 1 treatment of this standard.

+### Board in a rated assembly shall be installed with the edges and ends in moderate contact, and gaps at joints shall not exceed 1/8 in.

+### Where a rated partition is also sound-rated, the requirements of both tested assemblies shall be met, and where they conflict, the Contractor shall report the conflict to the Architect of Record before proceeding.

+### Rated partitions shall be labeled above the ceiling at not more than 30 ft along their length with the design number and the hourly rating, in lettering not less than 3 in. high, where [[parameter: adopted-building-code]] requires it.

+## Head-of-Wall and Base-of-Wall Joints {toc}

+### The joint between the top of a rated partition and the structure above, and the joint at its base where the floor is not level, shall be closed with the listed joint system that [[sync/firestopping]] furnishes for the rating and the movement of the partition.

+### Board shall be held clear of the deck flutes and the structure at the head of a rated partition by the distance the listed joint system requires, and the flutes above the runner shall not be filled with board or unlisted material by this trade.

+### The head-of-wall joint system is listed with the wall assembly, the deck profile, and a movement class, so a joint system that matches the wall but not the deck is not a listed condition; the board installer's job is to leave the gap the listing expects and nothing more. {note}

+## Control Joints in Rated Assemblies {toc}

+### Control joints in a fire-resistance-rated partition or membrane shall be installed under GA-234 with the backing the design number or GA-234 requires behind the joint.

+### The backing behind a rated control joint shall be continuous for the full height of the assembly and shall be attached to the framing on both sides of the joint.

+### A control joint cuts the face layer of a rated wall from top to bottom, and without backing behind the cut the wall has a slot through which fire passes; GA-234 is the tested detail that closes the slot without rigidly connecting the two sides. {note}

+## Area Separation Walls {toc}

+### Requirements in this article apply where area separation walls are selected in the datasheet field for the assemblies in scope.

+### An area separation wall is a fire wall between attached dwelling units or fire areas in light-frame construction, built as a freestanding two-hour assembly of two layers of 1 in. Type X shaftliner in steel H-studs, held to the framing on each side by aluminum breakaway clips; when one side burns, the clips soften and release, the burning structure falls away, and the wall stands on its own with the other side intact. {note}

+### Area separation walls shall be built to the design number cited for them on the partition schedule and under GA-620.

+### Shaftliner panels shall be 1 in. Type X shaftliner conforming to ASTM C1396, installed vertically in H-studs with the panel edges fully engaged in the stud webs and with horizontal joints staggered between the two layers as the design number states.

+### H-studs, top and bottom runners, and breakaway clips shall be the products the design number names, and the clips shall be installed at the spacing the design number states and shall be aluminum unless the design number names another material.

+### A clearance of not less than 3/4 in. shall be maintained between the shaftliner assembly and the framing on each side, and the clearance shall be kept free of blocking, board, and other material that would tie the framing to the wall.

+### The wall shall extend continuously from the foundation to the underside of the roof sheathing, with the parapet or the roof intersection built as the design number and the adopted building code require for a fire wall.

+### The mineral wool or other fill the design number requires in the clearance space at the roof and at floor lines shall be installed before the adjacent framing is closed.

+## Thermal Barrier Over Foam Plastic {toc}

+### Where gypsum board is the thermal barrier separating foam plastic insulation from the interior of the building, it shall be not less than 1/2 in. thick, shall be applied to the framing or furring over the foam plastic without gaps, and shall be fastened at the spacing [[parameter: adopted-building-code]] and the foam plastic manufacturer's evaluation report require.

+### The adopted building code requires foam plastic to be separated from the interior by a thermal barrier that delays its ignition, and 1/2 in. gypsum board is the prescriptive barrier the code names; the board over an insulated furred wall is doing that job whether or not anyone specified it, which is why the fastening and the continuity of that board are held to the code rather than to the finish. {note}

+# Sound-Rated Construction {toc}

+## Perimeter Acoustic Sealant {toc}

+### Requirements in this article apply where sound-rated partitions are selected in the datasheet field for the assemblies in scope.

+### The perimeter of each face of a sound-rated partition shall be sealed with acoustical sealant applied under ASTM C919 at the floor runner, at the head, at abutting walls and columns, and around every penetration and outlet.

+### Sealant shall be applied as a continuous bead under the floor and head runners before they are fastened, and as a continuous bead at the perimeter of each board layer before the next layer or the finish is applied.

+### Sealant shall be the non-hardening acoustical sealant furnished under [[sync/joint-sealants]], and a sealant that hardens or shrinks shall not be used at a sound-rated perimeter.

+### A gap of 1/8 in. along the base of a 10 ft partition is an opening of about 15 sq in., and an opening that size in a partition rated in the mid-50s passes more sound than the whole wall does; the sealant bead is the single lowest-cost component of the assembly and the one most often skipped. {note}

+### The cavity fill shall be in place and inspected under [[sync/acoustic-insulation]] before the closing face of a sound-rated partition is sealed.

+## Electrical Boxes in Sound-Rated Partitions {toc}

+### Requirements in this article apply where sound-rated partitions are selected in the datasheet field for the assemblies in scope.

+### Electrical boxes on opposite faces of a sound-rated partition shall be offset horizontally by not less than the distance indicated in the datasheet and shall not be installed in the same stud cavity.

+```datasheet

+label: Minimum Horizontal Offset Between Boxes on Opposite Faces

+type: range

+unit: in.

+options:

+ min: 0

+ max: 48

+ setpoints: [0, 12, 16, 24, 32, 48]

+default: 24

+```

+### An offset of 24 in. places the boxes in separate cavities at both 16 in. and 24 in. stud spacing and is the norm most sound-rated details show; a zero offset is the fixed head condition at a partition whose tested assembly carries putty-padded back-to-back boxes, and offsets larger than 24 in. buy a margin at partitions rated in the high 50s and above. {note}

+### The sealing of electrical boxes in sound-rated partitions shall be as indicated in the datasheet.

+```datasheet

+label: Sealing of Electrical Boxes in Sound-Rated Partitions

+type: radio

+options:

+ - "Putty pads on every box in a sound-rated partition"

+ - "Putty pads on boxes only where the tested assembly or the adopted code requires them"

+ - "Boxes sealed to the board with acoustical sealant without putty pads"

+```

+### Putty pads on every box add a few dollars per box and close the box as a sound path regardless of who cut the opening, which is the norm at partitions rated 50 and above; pads only where the listing requires them is the economy at a partition whose rating leaves margin for a few open boxes; and sealant alone closes the joint between the box and the board but not the box itself, and is the least effective of the three. {note}

+### Putty pads shall be the listed pads that, in a rated partition, are also required under [[sync/firestopping]] for the membrane penetration, and one pad shall serve both functions.

+### Openings cut in the board for boxes shall fit the box with not more than 1/8 in. clearance on any side, and the clearance shall be filled with acoustical sealant.

+## Flanking Paths {toc}

+### A sound-rated partition that stops at a suspended ceiling delivers the rating of the plenum path over it or of the partition, whichever is lower, and the plenum treatment for those partitions is furnished under [[sync/acoustic-insulation]]. {note}

+### Ducts, pipes, and conduit that pass through a sound-rated partition shall be sleeved or wrapped and sealed at both faces with acoustical sealant so that the annular space is closed.

+### A sound-rated partition shall extend to the underside of the structure above, or shall be paired with a plenum barrier or a rated ceiling, as the partition schedule shows, and shall not be terminated at a ceiling that the schedule shows it extending past.

+### Door and frame perimeter seals at openings in sound-rated partitions are furnished under [[sync/doors-frames-and-hardware]]. {note}

+# Board Application and Fastening {toc}

+## Application {toc}

+### Gypsum board shall be applied under ASTM C840 and GA-216 and, at rated and sound-rated assemblies, as the cited design number states.

+### Framing shall be plumb, level, and at the specified spacing before board is applied, and a stud that is bowed, twisted, or out of plane by more than 1/8 in. in 10 ft shall be corrected before boarding.

+### Board on walls shall be applied with the long edges perpendicular to the framing where the height permits, and where the board is applied parallel, the edges shall land on framing.

+### Board on ceilings shall be applied before board on walls, with the long edges perpendicular to the furring or joists.

+### Board shall be cut by scoring and snapping, or by sawing where the cut will be exposed, and cut edges shall be smoothed so that they seat against the adjacent board.

+### Ends and edges of the board shall be in moderate contact without forcing, and a gap wider than 1/4 in. at a joint in a non-rated assembly shall be prefilled with setting-type compound before taping.

+### Butt joints between board ends shall be staggered from those in adjacent courses and, on ceilings, shall be back-blocked or placed at a furring member.

+### Perpendicular application puts the tapered edges at the horizontal joints, where they are finished flat with the least compound, and reduces the number of butt joints, which are the joints that show; the exception is a wall taller than the board is long, where a parallel application puts every edge on a stud and the butt joints at the head, out of sight. {note}

+## Fasteners to Steel Framing {toc}

+### Screws for attaching board to steel framing shall be self-drilling, self-tapping bugle-head screws conforming to ASTM C1002 where the framing is not thicker than 33 mil and to ASTM C954 where it is thicker.

+### Screw length shall provide not less than 3/8 in. of penetration through the framing member for the total board thickness applied, and in multi-layer applications shall be selected for the layer being fastened.

+### Screws shall be spaced as ASTM C840 requires for the board thickness, the framing spacing, and the location on a wall or a ceiling, or as the cited design number states, whichever is closer.

+### Screws shall be placed not closer than 3/8 in. to the edge or end of the board and shall be driven so that the head is seated slightly below the board face without breaking the face paper.

+### Screws shall be driven starting at the center of each board and working toward the edges so that the board is drawn against the framing without buckling.

+### A screw driven through the paper has lost most of its holding power and every one of them pops a few months after the paint goes on; a screw left proud telegraphs through the compound, and the depth-setting nosepiece on a screw gun is the only thing between the two. {note}

+## Fastening to Wood Framing {toc}

+### Requirements in this article apply where partitions on wood framing are selected in the datasheet field for the assemblies in scope.

+### The fastening of board to wood framing shall be as indicated in the datasheet.

+```datasheet

+label: Fastening of Board to Wood Framing

+type: radio

+options:

+ - "Type W screws conforming to ASTM C1002"

+ - "Nails conforming to ASTM C514"

+ - "Adhesive conforming to ASTM C557 with screws or nails at reduced spacing"

+```

+### Screws hold in wood that shrinks and are the norm in commercial work, and a listed assembly on wood framing commonly states screws; nails are faster, are the norm in residential framing, and pop where the framing dries in service unless they are ring-shank; adhesive with reduced fastening cuts the fastener count on a plain wall and bridges a slightly irregular stud, and it is not admissible in a rated assembly unless the design number includes it and not usable over a vapor retarder or a faced insulation. {note}

+### Fasteners into wood shall penetrate the framing by not less than 5/8 in. for screws and 3/4 in. for nails, at the spacing ASTM C840 requires for the fastener and the location.

+### Board shall not be applied to wood framing whose moisture content exceeds 19 percent, and where the framing is wetter, application shall wait until it dries.

+## Multi-Layer Application {toc}

+### In multi-layer applications for fire resistance, sound rating, or abuse resistance, the base layer shall be fully fastened before the face layer is applied.

+### Face-layer joints shall be offset from base-layer joints by not less than one framing space in both directions, and the face layer at a corner shall lap the base layer of the adjoining wall.

+### Where the face layer is laminated to the base layer with adhesive, the adhesive shall be the product the design number or the board manufacturer names, applied in the pattern published for it, with the supplemental fasteners the design number states.

+### Adhesive alone shall not attach the face layer in a fire-resistance-rated assembly unless the design number includes and describes the adhesive application.

+### Laminating screws conforming to ASTM C1002 Type G shall be used only where the face layer is fastened to the base layer rather than to the framing, and only where the design number permits it.

+# Accessories and Trim {toc}

+## Accessory Standards {toc}

+### Corner bead, casing bead, edge trim, reveal trim, and control joints shall conform to ASTM C1047.

+### Accessories shall be fastened, crimped, clinched, stapled, or embedded as ASTM C840 and the accessory manufacturer publish for the accessory and the substrate.

+### Accessories shall be installed straight, plumb, level, and in one piece for the length of the run where the run does not exceed the stock length, with joints at splices tight and aligned.

+### Accessories of dissimilar metals shall not be joined where moisture could create a galvanic couple.

+### Accessories in a room with elevated humidity or intermittent wetting shall be rigid PVC, zinc alloy, or hot-dip galvanized steel, and paper-faced or electrogalvanized steel accessories shall not be installed there.

+## Corner Bead {toc}

+### Corner bead shall be installed at every exposed exterior corner of gypsum board and at every exposed board edge that meets another plane at an angle.

+### The material of the corner bead shall be as indicated in the datasheet.

+```datasheet

+label: Corner Bead Material

+type: select

+options:

+ - "Galvanized steel bead"

+ - "Paper-faced galvanized steel bead"

+ - "Rigid PVC bead"

+ - "Paper-faced rigid PVC bead"

+ - "Zinc alloy bead"

+```

+### Galvanized steel bead resists impact best and is fastened through its flanges, and its nose cracks the compound where a wall is struck repeatedly; paper-faced steel is embedded in compound and bonds to the board, so a struck corner dents without cracking the finish, which is why it is the norm on painted commercial walls; PVC does not rust and does not dent, and it bends at a heat gun for a curved corner; paper-faced PVC combines those properties at the highest cost per foot; and zinc alloy is the material for a wet room or an exterior soffit where a steel bead would rust through the paint. {note}

+### The profile of exposed corners shall be as indicated in the datasheet.

+```datasheet

+label: Exposed Corner Profile

+type: radio

+options:

+ - "Square corner"

+ - "Bullnose corner"

+ - "Chamfered corner"

+default: "Square corner"

+```

+### A square corner is the norm and takes any base, casing, and door frame without a transition piece; a bullnose is a rounded corner of 3/4 in. or larger radius that resists chipping and softens a corridor, and it requires a matching bullnose base, casing, and frame return at every trim it meets; a chamfered corner is a flat 45° face that shares the transition problem with bullnose and is furnished for a specific detail. {note}

+### The corners that receive a profile other than square shall be as indicated on [[drawing: the interior elevations]].

+## Casing Bead and Edge Trim {toc}

+### Casing bead or edge trim shall be installed wherever board terminates against a dissimilar material, at door and window frames that do not wrap the board, at columns, at masonry, and at any exposed edge that is not finished with corner bead or a tapered joint.

+### The material of casing bead and edge trim shall be as indicated in the datasheet.

+```datasheet

+label: Casing Bead and Edge Trim Material

+type: select

+options:

+ - "Galvanized steel"

+ - "Rigid PVC"

+ - "Zinc alloy"

+```

+### Galvanized steel is the norm for a dry, painted interior and is the least expensive; rigid PVC is furnished where the trim meets a wet room, a shower surround, or an exterior soffit and where a steel trim would rust; and zinc alloy is the metal trim for those same locations where a paintable metal edge is wanted. {note}

+### A sealant joint shall be provided between the casing bead and the dissimilar material where the joint will be exposed, and the sealant is furnished under [[sync/joint-sealants]].

+## Reveal and Shadow-Line Trim {toc}

+### Reveal trim and shadow-line trim shall be installed where a recessed joint or a shadow line is shown, plumb and level, in continuous runs, and finished to the same level as the adjacent board.

+### The locations, profiles, and reveal dimensions of reveal trim shall be as indicated on [[drawing: the interior elevations and the ceiling details]].

+### A reveal at a ceiling perimeter also serves as the perimeter relief of this standard where the ceiling board is held clear of the wall behind the trim. {note}

+# Control Joints {toc}

+## Control Joint Locations {toc}

+### Control joints shall be installed in partitions and ceilings at the locations ASTM C840 requires and at the locations shown on [[drawing: the interior elevations and the reflected ceiling plans]].

+### The maximum length of a partition between control joints shall be as indicated in the datasheet.

+```datasheet

+label: Maximum Partition Length Between Control Joints

+type: range

+unit: ft

+options:

+ min: 10

+ max: 30

+ setpoints: [10, 15, 20, 25, 30]

+default: 30

+```

+### ASTM C840 sets 30 ft as the maximum run of partition or ceiling without a control joint, and 30 ft is the norm; a tighter spacing is selected at a long unbroken corridor wall in a building with large seasonal humidity swing, at a wall on a long-span floor, or where the finish is a gloss paint that shows every hairline, and it costs a visible joint every time it is invoked. {note}

+### A control joint shall be installed where a partition or ceiling crosses a construction joint, an expansion joint, or a change in the supporting structure, and at each side of a change in framing direction.

+### A control joint shall be installed in a ceiling without perimeter relief where the run exceeds 30 ft in either direction or the area bounded by control joints exceeds 900 sq ft, and in a ceiling with perimeter relief where the run exceeds 50 ft or the area exceeds 2,500 sq ft.

+### A control joint shall be installed at the head of a door opening in a partition longer than the datasheet spacing, extending from the top corner of the frame to the ceiling or the structure, unless the opening is framed to the head with a continuous header stud.

+### A partition cracks where the movement concentrates, and the corner of a door opening is the stress riser in any long wall; a control joint run up from the frame head puts the crack where it is meant to be and hides it in a groove. {note}

+### Control joints shall not be installed in a rated assembly except as GA-234 and the Control Joints in Rated Assemblies article of this standard permit.

+## Control Joint Product and Installation {toc}

+### The material of control joints shall be as indicated in the datasheet.

+```datasheet

+label: Control Joint Material

+type: select

+options:

+ - "Zinc alloy control joint"

+ - "Rigid PVC control joint"

+ - "Galvanized steel control joint"

+```

+### Zinc alloy is the norm for control joints because it does not rust under the compound and its tape strip peels cleanly after finishing; rigid PVC is the joint for a wet room or an exterior soffit and can be bent for a curved run; and galvanized steel is the least expensive and is admissible where the joint stays dry and the finish is not a gloss that would show a rust stain. {note}

+### A control joint shall be a preformed section that leaves a continuous open groove of not less than 1/4 in. between the two faces of board, and a taped joint, a V-groove, or a scored line shall not be substituted for it.

+### Control joints shall be set plumb on walls and straight on ceilings, in continuous runs from the floor to the head of the partition or from edge to edge of the ceiling.

+### The board shall be cut through, and the framing behind the joint shall be interrupted or doubled, so that the two sides of the joint are free to move.

+### The flanges of the control joint shall be fastened to the board on each side, and compound shall be feathered over the flanges and shall not be applied into the groove.

+### The protective tape over the groove shall remain in place through finishing and painting and shall be removed after the final coat.

+### A control joint filled with compound or paint is a taped joint with a metal strip in it, and it cracks beside the strip within the first season. {note}

+## Perimeter Relief at Ceilings {toc}

+### Whether gypsum board ceilings are provided with perimeter relief shall be as indicated in the datasheet.

+```datasheet

+label: Perimeter Relief at Gypsum Board Ceilings

+type: radio

+options:

+ - "Perimeter relief, with the ceiling board held clear of the walls"

+ - "Ceiling board fastened to the perimeter walls"

+```

+### Perimeter relief holds the ceiling board about 1/4 in. clear of the walls behind a casing bead or a reveal trim, so that the ceiling moves with the structure above without cracking at the corner, and it raises the ceiling area permitted between control joints from 900 to 2,500 sq ft; a ceiling fastened at the perimeter finishes with a taped inside corner, which is cheaper per foot and is the norm in residential work and in small rooms where the area limit is never reached. {note}

+### Where perimeter relief is provided, the ceiling board shall not be fastened to the perimeter wall framing or to the wall angle, and the first ceiling fastener shall be not closer than 8 in. to the wall.

+### Where perimeter relief is provided in a rated horizontal membrane, the relief detail shall be one the design number permits.

+# Joint Treatment {toc}

+## Joint Compound and Tape {toc}

+### Joint compound shall conform to ASTM C475 and shall be a product the board manufacturer accepts for the board and the facing furnished.

+### The compound used to embed tape shall be as indicated in the datasheet.

+```datasheet

+label: Tape Embedment Compound

+type: radio

+options:

+ - "Setting-type compound"

+ - "Drying-type compound"

+```

+### Setting-type compound hardens by hydration, reaches its strength in a stated set time whether or not the air is dry, shrinks less, and bonds tape more strongly, which suits it to the embedment coat, to prefill, to back-blocking, and to work in a cold or humid space; it cannot be reworked once it sets and is harder to sand. Drying-type compound is a single product for every coat, sands easily, and is the choice of most crews for speed, and it is the one that fails to dry in a humid, unventilated space. {note}

+### Where glass fiber mesh tape is used, the embedment compound shall be setting-type compound regardless of the datasheet selection.

+### Joint tape shall conform to ASTM C475.

+### The joint tape shall be as indicated in the datasheet.

+```datasheet

+label: Joint Tape

+type: radio

+options:

+ - "Paper tape"

+ - "Glass fiber mesh tape"

+default: "Paper tape"

+```

+### Paper tape is the norm because it is strongest across the joint, folds cleanly at an inside corner, and is what the finish levels assume; glass fiber mesh tape is self-adhering and faster to place, is the tape for patching and for glass-mat and backer boards whose facing the paper tape does not bond to, and it depends on setting-type compound for its strength. {note}

+### Inside corners shall be taped with paper tape or a paper-faced corner tape, and mesh tape shall not be used at an inside corner.

+## Levels of Finish {toc}

+### The levels of finish are the six stages GA-214 and ASTM C840 define, from bare board through a skim-coated surface, and each level is a description of what has been done to the joints, the fasteners, and the accessories rather than a measure of quality; the level a surface needs is set by the decoration it will receive and the light that will fall on it, and the argument over whether a wall is acceptable is settled by naming the level before the work starts. {note}

+### In this standard the levels are understood as follows: {note}

+- Level 0: no taping, finishing, or accessories; the board is left as applied

+- Level 1: tape embedded in compound at every joint and inside corner, with the surface free of excess compound and with tool marks and ridges acceptable

+- Level 2: tape embedded and covered by a thin coat of compound, and fastener heads and accessories covered by one coat, with tool marks and ridges acceptable

+- Level 3: Level 2 plus one additional coat over the joints and inside corners and a second coat over fasteners and accessories, with the surface smooth and free of tool marks and ridges

+- Level 4: Level 3 plus a further coat over the flat joints and over fasteners and accessories, feathered and sanded, with inside corners at two coats

+- Level 5: Level 4 plus a skim coat over the entire surface so that the board face and the compound take paint alike

+### The finish level of exposed surfaces, where the room finish schedule does not state a different level for a surface, shall be as indicated in the datasheet.

+```datasheet

+label: Finish Level at Exposed Surfaces

+type: range

+unit: level

+options:

+ min: 0

+ max: 5

+ setpoints: [0, 1, 2, 3, 4, 5]

+default: 4

+```

+### Level 4 is the norm for a painted commercial interior because a flat or eggshell paint over it hides the difference between board and compound under ordinary lighting; Level 5 is required by gloss and semi-gloss paints, by thin wall coverings, by dark colors, and by any wall or ceiling that is lit by grazing light from a window or a wall washer, and it adds a full skim coat to every square foot; Level 3 is the surface under a heavy texture, Level 2 the surface behind tile or in a mechanical room, and Level 1 the concealed side of a rated wall. {note}

+### The finish level of concealed surfaces, including plenums, chases, and the concealed face of rated partitions, shall be as indicated in the datasheet.

+```datasheet

+label: Finish Level at Concealed Surfaces

+type: range

+unit: level

+options:

+ min: 0

+ max: 3

+ setpoints: [0, 1, 2, 3]

+default: 1

+```

+### The surfaces that receive a finish level other than the datasheet values shall be as indicated on [[drawing: the room finish schedule]].

+### Surfaces scheduled to receive a gloss or semi-gloss paint, a wall covering thinner than a Type II vinyl, or a critical lighting condition identified on the room finish schedule shall be finished to Level 5 regardless of the datasheet value.

+### Surfaces scheduled to receive a wall covering shall be finished to not less than Level 4.

+### Surfaces that will be tiled shall be finished to Level 2 with the joint treatment the backer manufacturer publishes for tile.

+### Where the parties disagree whether a surface meets its finish level, the Architect of Record shall make the initial determination by inspection under the lighting conditions in which the surface will be viewed in service.

+### The finished surface shall be inspected under the permanent lighting, or under temporary lighting placed where the permanent lighting will be, and not under construction lighting alone.

+### Construction lighting hung from the ceiling shines down a wall at an angle that hides joint telegraphing, and the same wall lit from a window or a wall washer at a grazing angle shows every ridge; a Level 5 finish approved under work lights is still the finish level the surface got, and the inspection lighting is what makes the approval mean anything. {note}

+## Level 5 Skim Material {toc}

+### The material of the Level 5 skim coat shall be as indicated in the datasheet.

+```datasheet

+label: Level 5 Skim Coat Material

+type: radio

+options:

+ - "Trowel- or roller-applied joint compound skim coat"

+ - "Spray-applied high-build primer-surfacer formulated for Level 5 finishing"

+```

+### A compound skim coat is applied by the taping crew, sanded, and primed like the rest of the wall, and it is the surface that a plaster-like flatness is built on; a spray-applied primer-surfacer is applied by the painting crew in one pass, is faster on a large area, and fills texture rather than leveling it, so it is the choice where the board and compound are already flat and the aim is uniform porosity under a gloss paint. {note}

+### Where a spray-applied primer-surfacer is selected, the product shall be one the board manufacturer and the paint manufacturer accept as a Level 5 surface, and its application shall be coordinated with [[sync/interior-painting]].

+## Finish at Rated Assemblies {toc}

+### The joint treatment a design number requires shall be applied to both faces of a rated assembly regardless of the finish level scheduled for either face.

+### A rated partition whose concealed face is above a ceiling shall receive on that face not less than the Level 1 treatment of this standard, or the treatment the design number states, whichever is greater.

+## Textured Finishes {toc}

+### The textured finish applied to gypsum board surfaces, where the room finish schedule calls for texture, shall be as indicated in the datasheet.

+```datasheet

+label: Textured Finish

+type: select

+options:

+ - "Smooth, with no applied texture"

+ - "Spray-applied orange peel texture"

+ - "Spray-applied knockdown texture"

+ - "Spray-applied sand or aggregate texture"

+ - "Hand-applied skip trowel texture"

+ - "Hand-applied smooth trowel finish"

+default: "Smooth, with no applied texture"

+```

+### Smooth is the norm in commercial work and the only surface a gloss paint or a wall covering accepts; orange peel is a fine spray that hides a Level 3 surface at the least cost and is the residential norm in much of the country; knockdown is a heavier spray flattened with a trowel that hides more and shows more dirt; a sand or aggregate texture hides the most and is the surface for a garage or a back-of-house ceiling; skip trowel and smooth trowel are hand-applied plaster-like finishes that cost as much as veneer plaster and are chosen for their appearance rather than for concealment. {note}

+### The surfaces that receive texture, and the pattern and density of the texture, shall be as indicated on [[drawing: the room finish schedule]].

+### A textured finish shall be applied over not less than a Level 3 surface for a heavy texture and not less than a Level 4 surface for a light texture, and the surface shall be primed before a spray texture is applied unless the texture manufacturer publishes application over unprimed board.

+### Texture shall be uniform in pattern, density, and thickness across each surface and from one surface to the next in a room, and the accepted sample or mock-up shall be the standard for uniformity.

+### A textured ceiling shall be applied only to board that the Ceiling Board article of this standard permits under a water-based texture at the framing spacing installed.

+# Patching and Tie-In to Existing Construction {toc}

+## Where new board meets retained construction under [[sync/selective-demolition]], the retained board shall be cut back to sound material at a framing member, and the new board shall be fastened to framing on both sides of the joint.

+## The joint between new and retained board shall be taped and finished to the level scheduled for the surface, and the finish shall be feathered onto the retained surface so that the joint does not read under the finish coat.

+## Where a retained assembly is fire-resistance-rated, the patch shall restore the board type, thickness, layers, and fastening the design number states, and the rating shall not be restored by compound or by unlisted material.

+## Where a retained assembly is sound-rated, the cavity fill and the perimeter sealant at the patch shall be reinstated before the patch is closed.

+## Holes and damaged areas in board that will be finished shall be patched with board of the same type and thickness, supported on framing or backing on all sides, and shall not be filled with compound alone where the opening exceeds 2 in. in any direction.

+# Delivery, Storage, and Handling {toc}

+## Gypsum panel products shall be delivered, stored, and handled under ASTM C1264 and the manufacturer's published instructions.

+## Board shall be delivered in the manufacturer's packaging and stored flat, on a level surface, off the floor, indoors, and protected from weather, moisture, and direct sunlight.

+## Board shall not be stored on edge except for the brief period of moving it to its point of installation.

+## Board stacked flat on an uneven surface takes the shape of the surface, and board stored on edge sags at the center, and neither returns to flat when it is hung; board stacked in the middle of a floor span in one pile also loads the floor beyond what most floors were designed for, which is why bundles are spread along bearing walls. {note}

+## Board shall be stacked in piles that do not exceed the floor's design capacity and shall be distributed along bearing lines rather than at the center of a span.

+## Board that is wet, that has a delaminated facing, a crushed edge, or a soft core, or that shows mold growth shall be removed from the site.

+## Framing members shall be stored off the ground and protected from water, and members with red rust that has pitted the steel shall be rejected.

+## Joint compound, adhesive, and sealant shall be stored above freezing and shall not be used after the manufacturer's stated shelf life.

+# Warranty {toc}

+## The Contractor shall warrant the gypsum board work, including the framing, fastening, blocking, joint treatment, finish, and texture, against defects in materials and workmanship for the period indicated in the datasheet, measured from the date of substantial completion.

+```datasheet

+label: Installation Warranty Period

+type: range

+unit: years

+options:

+ min: 1

+ max: 5

+ setpoints: [1, 2, 3, 5]

+default: 1

+```

+## Defects covered by the warranty include fastener pops, joint ridging, joint cracking, bead delamination, nail or screw telegraphing, sagging ceiling board, texture inconsistency, and cracking caused by the omission or incorrect installation of control joints, perimeter relief, or deflection heads.

+## Hairline cracking at joints that results from seasonal movement of the structure is not a defect where control joints, perimeter relief, and deflection heads were installed as this standard requires. {note}

+## The warranty shall not cover damage from water entering the building after acceptance, from structural movement beyond the movement capacity the contract documents state, from loads applied by others, or from work by others that opened or altered the assembly.

+## Where the contract documents state a longer warranty period than the datasheet, the longer period shall govern.

+## The Contractor's cost of a warranty correction shall include the removal and replacement of finishes over the defect, the restoration of any rated or sound-rated assembly disturbed, and the refinishing of the surface to its scheduled level and texture.

+## Work performed under this warranty shall itself be warranted for a full new term equal to the original period measured from the date the correction is completed, or for the remainder of the original period, whichever ends later.

+## Where the Contractor observes a condition during the work that will shorten the life of the gypsum board assemblies, including water entry, an unconditioned interior, structural deflection greater than the deflection head was built for, or another trade defeating a deflection head or a control joint, the Contractor shall report it to the Architect of Record in writing before the affected assembly is closed.

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