+---
+title: Suspended Acoustical Ceilings
+category: Architectural
+toc_depth: 3
+description: >
+ When to use: Direct-hung metal suspension grid systems and acoustical panels or tiles — both exposed-tee lay-in and concealed-spline — for commercial, institutional, healthcare, educational, and hospitality interiors. Covers the suspension grid (type, profile, duty classification, and finish), acoustical panels (material, size, edge detail, and surface texture), acoustical performance (NRC and CAC), light reflectance, surface-burning fire performance, fire-resistance-rated ceiling membrane assemblies, seismic restraint and perimeter treatment, hold-down clips, trim and moldings, hanger wire and bracing, and integration with light fixtures, air devices, and sprinkler heads.
+ Not intended for: Gypsum board ceilings, whether suspended or directly attached (see [[sync/gypsum-board-assemblies]]); specialty linear metal, open-cell, wood, baffle, and stretched-fabric ceiling systems; integrated luminous and access-floor-style ceiling systems; exterior soffit ceilings exposed to weather; acoustic wall treatments and freestanding sound-absorptive panels; the structural deck or framing from which the ceiling is hung; and the light fixtures, diffusers, and sprinkler heads themselves, which are specified under their respective standards and only coordinated here.
+---
+
+# Scope
+
+This standard governs the materials, performance, and installation of direct-hung suspended acoustical ceiling systems, comprising a metal suspension grid hung from the structure above and the acoustical panels or tiles it carries. Suspended acoustical ceilings are the dominant ceiling system in commercial interiors because they conceal the structure, ductwork, piping, and wiring in the plenum above while providing an accessible, demountable surface that absorbs sound within the room, attenuates sound between rooms sharing a plenum, distributes light, and integrates the lighting, air distribution, and fire suppression that the occupied space requires. The system is valued precisely because every panel lifts out for access — a property that distinguishes it from the monolithic gypsum board ceiling and that shapes nearly every requirement in this standard.
+
+A suspended acoustical ceiling is a system, not a collection of independent parts. The grid carries the panels; the panels rest in or engage the grid; the hanger wires carry the grid; and in a seismic event or a fire, the grid, the panels, the perimeter, the bracing, and every penetrating fixture must act together as designed. The acoustical performance the occupant experiences depends jointly on the panel's sound-absorption rating, the panel's plenum attenuation rating, the integrity of the perimeter seal, and the treatment of every penetration. The Contractor shall treat the ceiling as an assembly and shall coordinate the grid layout, the panel module, the seismic design, and the locations of all penetrating items before any grid is hung.
+
+Coordinate gypsum board ceilings and the gypsum board soffits and bulkheads that frame acoustical ceiling fields with [[sync/gypsum-board-assemblies]]. Coordinate the recessed light fixtures that occupy grid modules with [[sync/lighting-fixtures]], the air diffusers and return grilles with [[sync/hvac-air-distribution-devices]], and the sprinkler heads that penetrate the ceiling plane with [[sync/wet-pipe-fire-sprinkler-systems]]. Where the ceiling forms part of a fire-resistance-rated floor-ceiling or roof-ceiling assembly, coordinate the rated membrane requirements with the fire-resistance design number; this standard governs the ceiling membrane within that assembly but not the structural framing above it.
+
+# Referenced Standards
+
+All materials, suspension systems, and installation shall comply with the latest edition adopted by the Authority Having Jurisdiction for each of the following standards. 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.
+
+| Standard | Title |
+|----------|-------|
+| ASTM C635/C635M | Standard Specification for the Manufacture, Performance, and Testing of Metal Suspension Systems for Acoustical Tile and Lay-in Panel Ceilings |
+| ASTM C636/C636M | Standard Practice for Installation of Metal Ceiling Suspension Systems for Acoustical Tile and Lay-in Panels |
+| ASTM E580/E580M | Standard Practice for Installation of Ceiling Suspension Systems for Acoustical Tile and Lay-in Panels in Areas Subject to Earthquake Ground Motions |
+| ASTM E1264 | Standard Classification for Acoustical Ceiling Products |
+| ASTM C423 | Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberation Room Method |
+| ASTM E1414/E1414M | Standard Test Method for Airborne Sound Attenuation Between Rooms Sharing a Common Ceiling Plenum |
+| ASTM E84 | Standard Test Method for Surface Burning Characteristics of Building Materials |
+| ASTM E119 | Standard Test Methods for Fire Tests of Building Construction and Materials |
+| ASTM E1477 | Standard Test Method for Luminous Reflectance Factor of Acoustical Materials by Use of Integrating-Sphere Reflectometers |
+| ASTM A641/A641M | Standard Specification for Zinc-Coated (Galvanized) Carbon Steel Wire |
+| ASCE/SEI 7 | Minimum Design Loads and Associated Criteria for Buildings and Other Structures |
+| CISCA | Ceilings and Interior Systems Construction Association — Seismic Recommendations for Direct-Hung Suspended Ceiling Assemblies |
+| IBC | International Building Code (current edition adopted by jurisdiction) |
+| UL Fire Resistance Directory | UL Fire-Resistance Rated Floor-Ceiling and Roof-Ceiling Designs |
+
+ASTM E1264 is the classification framework that ties the others together: it defines the panel types, patterns, fire classes, and the acoustical and reflectance properties by which acoustical ceiling products are described, and it references ASTM C423 for sound absorption, ASTM E1414 for plenum attenuation, ASTM E84 for surface burning, and ASTM E1477 for light reflectance. ASTM C635 classifies the suspension system by structural duty; ASTM C636 governs how it is installed in ordinary conditions; and ASTM E580 governs how it is installed where earthquake ground motions apply, in coordination with the seismic design category established under ASCE/SEI 7 and adopted by the IBC.
+
+# Submittals
+
+## Action Submittals
+
+The Contractor shall submit the following for the Architect's review prior to procurement and installation. Installation shall not begin until the submittals have been reviewed and returned.
+
+- Product data for the suspension system, including the ASTM C635 structural duty classification, profile face width, web height, finish, and the manufacturer's load and deflection data
+- Product data for each acoustical panel type, including material, nominal size, thickness, edge detail, surface texture and pattern, ASTM E1264 type and pattern classification, NRC per ASTM C423, CAC per ASTM E1414, light reflectance per ASTM E1477, surface-burning class per ASTM E84, and any humidity or sag-resistance rating
+- A reflected ceiling plan coordination drawing showing grid layout, panel module, centering, border conditions, and the location of every light fixture, air device, sprinkler head, speaker, and access panel
+- Seismic design data for the ceiling system in Seismic Design Categories C through F, including the perimeter detail, bracing layout, hanger and brace spacing, and any required separation joints, prepared in conformance with ASTM E580 and the project's seismic design category
+- Samples of each acoustical panel type, minimum 12 inches square, with the edge detail visible, and a sample of each grid profile and finish
+- Identification of the specific UL or tested fire-resistance design number for every fire-resistance-rated floor-ceiling or roof-ceiling assembly that incorporates the acoustical ceiling as a rated membrane, cross-referenced to each ceiling type designation
+
+```datasheet
+label: Action Submittals Required
+type: checkbox
+options:
+ - "Product data — suspension system (duty, profile, finish, load data)"
+ - "Product data — acoustical panels (all types)"
+ - "Reflected ceiling plan coordination drawing"
+ - "Seismic design data (SDC C through F)"
+ - "Panel and grid samples"
+ - "Fire-resistance design number schedule (rated assemblies)"
+default: "Product data — suspension system (duty, profile, finish, load data)"
+```
+
+## Closeout Submittals
+
+- Warranty documentation for the suspension system and acoustical panels
+- Maintenance data describing recommended cleaning methods for the panel finish, and the manufacturer's instructions for replacing panels without damaging adjacent panels or the grid
+- A record of any field substitution to a fire-resistance design number, approved in writing by the Architect of Record
+
+# Quality Assurance
+
+## Installer Qualifications
+
+Acoustical ceiling installation shall be performed by workers experienced in the installation of direct-hung suspension systems of the type and duty class required on this project. Where the ceiling is installed in a Seismic Design Category that triggers ASTM E580 requirements, the installer shall be familiar with the specific seismic detailing — perimeter clearance, bracing, and separation joints — because seismic ceiling performance depends entirely on details that an installer accustomed only to non-seismic work will omit.
+
+## Single-Source Responsibility
+
+The suspension system and the acoustical panels should be obtained as a coordinated system in which the panel module, edge detail, and grid profile are designed to fit together. Mismatched grid and panel components — a tegular panel edge that does not seat correctly on a particular grid bulb, or a 9/16-inch panel rabbet on a 15/16-inch grid face — produce uneven reveals, panels that do not lie flat, and a finished ceiling that looks defective even when every part conforms to its own specification. The Contractor shall confirm that the grid profile and the panel edge detail are a matched set.
+
+## Mock-Up
+
+```datasheet
+label: Mock-Up Required
+type: radio
+options:
+ - "Yes — one representative ceiling bay including grid, panels, and one penetrating fixture"
+ - "No"
+default: "No"
+```
+
+Where a mock-up is required, the Contractor shall install one representative ceiling bay at a location directed by the Architect, demonstrating the grid finish, the panel edge reveal, the border panel condition, the perimeter trim, and the integration of one light fixture and one air device. The mock-up shall remain in place for review before production installation proceeds and may be incorporated into the work if approved.
+
+## Fire-Rated Assembly Listing
+
+Where the acoustical ceiling forms the membrane of a fire-resistance-rated floor-ceiling or roof-ceiling assembly, the complete assembly — structural framing, suspension system, panels, hold-down clips, and any required protection at penetrations — shall conform to a tested design listed by a Nationally Recognized Testing Laboratory or published in a recognized fire-resistance directory. The fire-resistance rating is a property of the tested assembly as a whole; substituting a panel, omitting hold-down clips, or changing the grid can invalidate the rating. The Contractor shall verify that every component matches the cited design number before procurement.
+
+# Environmental and Service Conditions
+
+## Sequence After Wet Work
+
+Acoustical panels shall not be installed until all wet work in the space — concrete, masonry, plaster, gypsum board finishing, and painting — is complete and dry, the building is enclosed and weathertight, and the permanent HVAC system is operating and maintaining the service-range temperature and humidity. Mineral fiber and most acoustical panels absorb moisture, and panels installed before the space is dry will sag, warp, or develop visible dimensional change as the building dries. The grid may be hung earlier where it does not interfere with other wet work, but panel installation shall wait for stable conditions.
+
+## Service Temperature and Humidity
+
+```datasheet
+label: Service Environment Humidity Condition
+type: radio
+options:
+ - "Standard interior — controlled temperature and humidity, sag resistance not critical"
+ - "Elevated humidity — high-humidity sag-resistant panels required (kitchens, natatorium-adjacent, humid climates)"
+ - "Continuously high humidity / washdown — non-mineral panel (fiberglass or metal) required"
+default: "Standard interior — controlled temperature and humidity, sag resistance not critical"
+```
+
+Standard mineral fiber panels are dimensionally stable within the normal occupied range of interior temperature and relative humidity. In spaces subject to elevated humidity — interior areas adjacent to pools, commercial kitchens, locker rooms, and projects in humid climates where the HVAC may not be continuously operated — panels with an enhanced sag-resistance rating shall be specified, because a standard panel that absorbs moisture sags visibly between grid members and will not recover. In continuously wet or washdown environments, mineral fiber panels shall not be used at all; fiberglass, coated metal, or other non-hygroscopic panels are required.
+
+# Suspension System
+
+## Structural Duty Classification
+
+```datasheet
+label: Suspension System Duty Classification (ASTM C635)
+type: radio
+options:
+ - "Light-duty — panels only, no anticipated fixture loads (residential, light commercial)"
+ - "Intermediate-duty — anticipated light fixtures and air diffusers (ordinary commercial)"
+ - "Heavy-duty — heavy fixtures, frequent access, or where required by seismic design"
+drawing_ref: true
+default: "Intermediate-duty — anticipated light fixtures and air diffusers (ordinary commercial)"
+```
+
+ASTM C635 classifies metal suspension systems as light-duty, intermediate-duty, or heavy-duty based on the load-carrying capacity of the main runners — specifically the maximum uniformly distributed load a simply supported four-foot main runner section can carry without mid-span deflection exceeding 1/360 of the span. Intermediate-duty is the appropriate default for ordinary commercial ceilings that carry recessed lay-in light fixtures and air diffusers. Heavy-duty systems shall be used where the ceiling carries heavier fixtures, where frequent panel removal and reinstallation is expected, or where the seismic design requires the additional stiffness and connection strength of a heavy-duty grid. Light-duty systems are limited to ceilings carrying nothing but the panels themselves.
+
+## Grid Exposure Type
+
+```datasheet
+label: Grid Exposure Type
+type: radio
+options:
+ - "Exposed tee — inverted-tee grid visible below the panel plane (lay-in)"
+ - "Concealed — grid hidden by kerfed or splined panels (concealed-spline)"
+drawing_ref: true
+default: "Exposed tee — inverted-tee grid visible below the panel plane (lay-in)"
+```
+
+An exposed-tee system uses an inverted-tee grid whose bulb and flange remain visible below the panel, with panels laid into the grid from above; it is the predominant commercial system because any panel lifts out for plenum access without disturbing its neighbors. A concealed system hides the grid behind kerfed panels that engage a spline, producing a monolithic appearance but requiring panels to be slid and unkeyed in sequence for access, which makes plenum work slower and risks panel damage. Exposed-tee is the default for almost all commercial work; concealed systems are reserved for spaces where the uninterrupted ceiling plane is an architectural objective and frequent plenum access is not expected.
+
+## Exposed-Tee Face Width and Profile
+
+```datasheet
+label: Exposed Grid Face Width
+type: radio
+unit: in
+options:
+ - "15/16 in — standard exposed tee"
+ - "9/16 in — narrow / slimline exposed tee"
+ - "Bolt-slot / interlocking profile (where specified for fixture or seismic engagement)"
+drawing_ref: true
+default: "15/16 in — standard exposed tee"
+```
+
+The 15/16-inch face is the standard exposed-tee profile and is the most widely stocked and most economical, with the broadest selection of compatible panels, trim, and fixture interfaces. The 9/16-inch narrow face produces a finer, more refined grid line favored in higher-finish interiors but requires panels with a matching narrower rabbet and offers a smaller selection. The bolt-slot or interlocking profile is specified where positive mechanical engagement between runners is needed for fixture support or seismic performance. The grid face width and the panel edge detail are interdependent and shall be selected together.
+
+## Grid Finish and Color
+
+```datasheet
+label: Grid Finish / Color
+type: radio
+options:
+ - "White (standard baked-enamel cap)"
+ - "Black"
+ - "Custom color — match architectural selection"
+ - "Aluminum / metallic"
+drawing_ref: true
+default: "White (standard baked-enamel cap)"
+```
+
+The exposed grid cap shall have a factory-applied baked-enamel or equivalent durable finish. White is the standard selection and coordinates with the white panel finish that dominates commercial work. Black grid is specified for theaters, audiovisual spaces, and design-driven interiors where the grid is intended to recede visually. Custom colors and metallic finishes shall match the architectural color selection. The grid finish shall be consistent across the entire ceiling field and matched at trim and moldings.
+
+## Hanger Wire
+
+```datasheet
+label: Hanger Wire Gauge
+type: radio
+unit: in
+options:
+ - "12 gauge (0.106 in) galvanized soft-temper wire — standard"
+ - "10 gauge (0.135 in) — where hanger spacing or load exceeds standard limits"
+default: "12 gauge (0.106 in) galvanized soft-temper wire — standard"
+```
+
+Hanger wire shall be galvanized, soft-temper carbon steel wire conforming to ASTM A641. Twelve-gauge wire is the standard for ordinary acoustical ceilings, where each wire supports no more than the area allowed by ASTM C636. Heavier ten-gauge wire shall be used where the load carried by each hanger exceeds the standard limit or where local conditions require wider hanger spacing. Hanger wire shall be hung plumb; wires that splay more than one in six from vertical do not carry their rated vertical load and shall be counter-sloped with an opposing wire or replaced with a rigid hanger.
+
+# Acoustical Panels
+
+## Panel Material
+
+```datasheet
+label: Panel Material
+type: radio
+options:
+ - "Mineral fiber — standard commercial, best CAC and fire performance per cost"
+ - "Fiberglass (glass wool) — high NRC, moisture-resistant, lower CAC"
+ - "Metal (perforated, with acoustic backing) — durable, washable, design-forward"
+ - "Wood (acoustically perforated or slotted) — architectural feature applications"
+drawing_ref: true
+default: "Mineral fiber — standard commercial, best CAC and fire performance per cost"
+```
+
+Mineral fiber is the standard panel material for commercial ceilings, offering balanced sound absorption, good plenum attenuation, reliable Class A surface burning, and the lowest cost; it is hygroscopic and is unsuitable for continuously wet locations. Fiberglass panels achieve the highest NRC values and resist moisture but generally provide lower plenum attenuation and require a fabric or membrane facing for cleanability. Metal panels with concealed acoustic backing are durable, washable, and used in healthcare, laboratory, and high-design spaces. Wood panels are reserved for architectural feature ceilings and require coordination of fire performance and acoustic backing. The material drives nearly every downstream property and shall be selected first.
+
+## Panel Module Size
+
+```datasheet
+label: Panel Module Size
+type: radio
+unit: in
+options:
+ - "24 x 24 in"
+ - "24 x 48 in"
+ - "Custom module — as indicated on reflected ceiling plan"
+drawing_ref: true
+default: "24 x 24 in"
+```
+
+The 24-by-24-inch module is the most common in current commercial work because it presents a finer, more contemporary grid pattern and accommodates two-by-two fixtures and air devices. The 24-by-48-inch module uses fewer panels and fewer cross runners and remains common in utilitarian and renovation work matching an existing two-by-four field. The module shall be coordinated with the light fixture and air device modules on the reflected ceiling plan so that fixtures and panels share a consistent grid.
+
+## Panel Edge Detail
+
+```datasheet
+label: Panel Edge Detail
+type: radio
+options:
+ - "Square lay-in — panel rests flush on exposed grid flange (standard)"
+ - "Tegular (reveal) — panel face drops below grid, recessed reveal at edge"
+ - "Concealed — kerfed edge engages concealed spline grid"
+drawing_ref: true
+default: "Square lay-in — panel rests flush on exposed grid flange (standard)"
+```
+
+A square lay-in edge rests flat on the grid flange and is the simplest and most economical detail, leaving the full grid face exposed flush with the panel. A tegular edge is rabbeted so the panel face drops below the grid flange, producing a shadow reveal that visually separates each panel and de-emphasizes the grid; it is widely used in offices and institutional spaces for a more finished appearance and requires a panel and grid designed for the reveal depth. A concealed edge is kerfed to engage a concealed-spline grid and is used only with concealed systems. The edge detail shall match the grid profile selected above.
+
+## Noise Reduction Coefficient (NRC)
+
+```datasheet
+label: Noise Reduction Coefficient (NRC) — minimum
+type: range
+unit: NRC
+options:
+ min: 0.50
+ max: 0.95
+ step: 0.05
+drawing_ref: true
+default: 0.70
+```
+
+The Noise Reduction Coefficient, determined per ASTM C423, expresses how much sound the panel absorbs within the room — the average absorption coefficient at 250, 500, 1000, and 2000 Hz, rounded to the nearest 0.05. A higher NRC reduces reverberation and improves speech clarity within the space. Open-plan offices, classrooms, and other spaces where occupants must hear and be heard benefit from high NRC values; an NRC of 0.70 is a reasonable default for general commercial work, while spaces with demanding speech-intelligibility goals warrant 0.80 or higher. NRC measures absorption within a room and shall not be confused with plenum attenuation between rooms, which is a separate property.
+
+## Ceiling Attenuation Class (CAC)
+
+```datasheet
+label: Ceiling Attenuation Class (CAC) — minimum
+type: select
+drawing_ref: true
+options:
+ - "Not specified — open-plan or non-sensitive area"
+ - "CAC 25 — minimum for general separation"
+ - "CAC 30"
+ - "CAC 35 — recommended for closed offices with shared plenum"
+ - "CAC 40+ — confidential / privacy-sensitive (medical, HR, legal)"
+default: "CAC 35 — recommended for closed offices with shared plenum"
+```
+
+The Ceiling Attenuation Class, determined per ASTM E1414, measures how well the panel blocks sound traveling from one room up through the plenum and back down into an adjacent room over a partition that stops at the ceiling. CAC matters wherever closed rooms share a common plenum and speech privacy is required — private offices, exam rooms, conference rooms, and human-resources or legal spaces. High-NRC panels frequently have low CAC and vice versa, because the properties that absorb sound differ from those that block its transmission; where both within-room acoustics and between-room privacy matter, a panel that balances the two, or a full-height partition that closes the plenum, is required. Specifying a high NRC alone does not provide speech privacy between rooms.
+
+## Light Reflectance
+
+```datasheet
+label: Light Reflectance (LR) — minimum
+type: range
+unit: LR
+options:
+ min: 0.75
+ max: 0.90
+ step: 0.01
+drawing_ref: true
+default: 0.85
+```
+
+Light reflectance, determined per ASTM E1477, is the fraction of incident visible light the panel surface reflects. A high light reflectance allows the ceiling to redistribute both daylight and electric light into the space, improving uniformity and reducing the connected lighting load needed to reach a target illuminance. A minimum light reflectance of 0.85 is a common and cost-effective default for white panels and supports energy-efficient lighting design. The Architect shall coordinate the reflectance value with the lighting design where daylighting credits or reduced lighting power density are objectives.
+
+## Surface-Burning Fire Performance
+
+```datasheet
+label: Surface Burning Characteristics (ASTM E84)
+type: radio
+options:
+ - "Class A — flame spread index 25 or less, smoke developed index 450 or less"
+ - "Class B — flame spread index 26 to 75"
+drawing_ref: true
+default: "Class A — flame spread index 25 or less, smoke developed index 450 or less"
+```
+
+Acoustical panels shall have surface-burning characteristics determined by ASTM E84. Class A — flame spread index of 25 or less and smoke developed index of 450 or less — is required by building codes for ceiling finishes in most occupied commercial spaces and shall be the default. The flame spread and smoke developed indices are properties of the panel material and finish; the Contractor shall confirm the panel's classification on the product data. Where the ceiling encloses a plenum used for environmental air, the more restrictive plenum requirements of the code shall be confirmed against the panel's tested values.
+
+## Fire-Resistance-Rated Ceiling Membrane
+
+```datasheet
+label: Fire-Resistance-Rated Floor/Roof-Ceiling Assembly
+type: radio
+options:
+ - "Not rated — ceiling is a finish, not a rated membrane"
+ - "Rated — ceiling is the membrane of a tested floor-ceiling or roof-ceiling assembly"
+drawing_ref: true
+default: "Not rated — ceiling is a finish, not a rated membrane"
+```
+
+Most acoustical ceilings are finishes that carry no fire-resistance rating of their own. Where the drawings designate the ceiling as the protective membrane of a fire-resistance-rated floor-ceiling or roof-ceiling assembly tested under ASTM E119, the entire assembly — including the specific panel, the grid, the hold-down clips, and the protection at every penetration — shall conform to the cited tested design number. The Contractor shall not substitute any component of a rated assembly and shall provide hold-down clips and penetration protection exactly as the design number requires, because the rating is lost if the ceiling membrane is disturbed in a fire and the panels fall away.
+
+# Seismic Restraint
+
+## Seismic Design Category and Applicable Practice
+
+```datasheet
+label: Seismic Design Category (SDC) — Ceiling
+type: select
+drawing_ref: true
+options:
+ - "SDC A or B — no seismic ceiling requirements beyond standard installation"
+ - "SDC C — ASTM E580 Category C requirements apply"
+ - "SDC D, E, or F — ASTM E580 Category D/E/F requirements apply"
+default: "SDC D, E, or F — ASTM E580 Category D/E/F requirements apply"
+```
+
+The seismic design category for the building and its components is established under ASCE/SEI 7 as adopted by the IBC and shall be shown on the drawings. In Seismic Design Categories A and B, no special ceiling seismic requirements apply beyond ASTM C636 installation. In Seismic Design Category C, the Category C provisions of ASTM E580 apply. In Seismic Design Categories D, E, and F, the more stringent Category D/E/F provisions of ASTM E580 apply, including heavier perimeter conditions, bracing, and separation joints. The Contractor shall install the ceiling to the practice that corresponds to the project's seismic design category, and shall not apply a lower category's details to a higher-category project.
+
+## Perimeter Clearance and Closure
+
+```datasheet
+label: Seismic Perimeter Detail (SDC D/E/F)
+type: radio
+options:
+ - "Two adjacent walls fixed, two opposite walls free with wide molding and clearance"
+ - "Perimeter restraint clips at all walls with seismic separation joints in field"
+ - "Not applicable — SDC A/B/C"
+drawing_ref: true
+default: "Two adjacent walls fixed, two opposite walls free with wide molding and clearance"
+```
+
+In higher seismic design categories, ASTM E580 requires the ceiling grid to be attached at two adjacent walls and left free to move at the two opposite walls, with a wide perimeter molding that provides clearance so the grid can move during an earthquake without binding against the wall and buckling. The required clearance at the free edges shall be provided by the wide molding indicated on the drawings, and the grid ends shall not be allowed to contact the wall closure. Where the ceiling area exceeds the limits of ASTM E580, seismic separation joints shall divide the field into independently braced areas. The perimeter detail shall be as shown on the [[drawing: reflected ceiling plan and seismic details]].
+
+## Lateral Bracing and Vertical Restraint
+
+In Seismic Design Categories D, E, and F, the ceiling shall be laterally braced with splay-wire bracing assemblies and rigid vertical compression struts at the spacing required by ASTM E580 and the project seismic design, so that the ceiling does not swing laterally and the grid is held down against vertical acceleration. Bracing shall be installed at the locations shown on the seismic details and shall not conflict with ductwork, piping, or fixtures in the plenum; the Contractor shall coordinate brace locations with the other plenum trades during the coordination-drawing phase, not in the field after conflicts arise.
+
+## Hold-Down Clips
+
+```datasheet
+label: Panel Hold-Down Clips
+type: radio
+options:
+ - "Required — at all panels (seismic SDC D/E/F, or where required by fire-rated design)"
+ - "Required — at light fixtures and air devices only"
+ - "Not required"
+drawing_ref: true
+default: "Required — at all panels (seismic SDC D/E/F, or where required by fire-rated design)"
+```
+
+Hold-down clips secure lay-in panels to the grid so they do not lift, shift, or fall out of the grid under vertical seismic acceleration, plenum pressure differential, or, in a rated assembly, the upward thrust of a fire. Clips shall be provided where the seismic design category requires them, where the fire-resistance design number requires them, and where the plenum operates at a pressure that could lift unrestrained panels. In Seismic Design Categories D, E, and F, hold-down clips are typically required at every panel; where the panel weight and conditions allow, clips may instead be required only at panels carrying or adjacent to fixtures.
+
+# Trim and Moldings
+
+## Perimeter Molding
+
+Perimeter wall molding shall be installed at every edge where the ceiling meets a wall, soffit, column, or other vertical surface, in the profile and finish that match the seismic and architectural requirements. In non-seismic conditions a standard angle or channel molding closes the edge; in higher seismic design categories the wide molding required for clearance under ASTM E580 shall be used at the free edges. Molding shall be installed level and the corners shall be neatly mitered or coped for a finished appearance.
+
+```datasheet
+label: Perimeter Molding Profile
+type: radio
+options:
+ - "Standard wall angle (L-molding)"
+ - "Channel / hemmed angle molding"
+ - "Wide seismic molding (clearance at free edges, SDC D/E/F)"
+ - "Shadow-line / reveal molding (architectural)"
+drawing_ref: true
+default: "Standard wall angle (L-molding)"
+```
+
+## Transitions and Trim at Penetrations
+
+Trim shall be provided at changes in ceiling height, at the edges of soffits and bulkheads, around columns, and at the borders of acoustical fields meeting gypsum board ceilings. Edge trim and closure pieces shall match the grid finish. Trim and closures around penetrating items shall be neat and tight, and shall not leave open gaps that compromise the ceiling's plenum attenuation or its appearance.
+
+# Testing and Inspection
+
+The Authority Having Jurisdiction and the Owner's representative shall have the right to inspect the suspension system, the hanger and bracing layout, and the perimeter and seismic details before panels are installed and before the ceiling is concealed by finishes. Where the ceiling forms a fire-resistance-rated membrane, the rated assembly shall be inspected and approved before it is enclosed. Where field acoustic verification is specified, an independent accredited testing agency shall measure the installed performance and report to the Owner.
+
+```datasheet
+label: Field Acoustic Verification Required
+type: radio
+options:
+ - "Yes — independent accredited testing agency"
+ - "No"
+default: "No"
+```
+
+# Installation
+
+## Layout and Centering
+
+The grid shall be laid out from the centerlines of the space so that border panels at opposite walls are equal in width and no border panel is less than half a full module wide, unless the reflected ceiling plan dictates a different layout for coordination with fixtures or architectural features. A ceiling with a full panel at one wall and a narrow sliver at the opposite wall looks unbalanced and is the most common avoidable defect in acoustical ceiling work. The Contractor shall establish the grid layout from the [[drawing: reflected ceiling plan]] and shall center the field as shown; where the plan does not dictate, the field shall be centered to equalize opposite borders.
+
+## Suspension and Hanger Spacing
+
+The suspension system shall be installed in conformance with ASTM C636 and, where applicable, ASTM E580. Main runners shall be spaced at not more than 4 feet on center, hanger wires along each main runner shall be spaced at not more than 4 feet on center, and the ceiling area supported by any single hanger wire shall not exceed 16 square feet. Hangers shall be attached only to the structure or to structural members designed to carry the ceiling load, never to ductwork, piping, conduit, or other non-structural items in the plenum. The first hanger at the end of each main runner shall be located within the distance of the end required by ASTM C636 so the runner end does not droop.
+
+## Independent Support of Fixtures and Devices
+
+Light fixtures, air diffusers, return grilles, and other items that occupy or penetrate the ceiling shall be supported so their weight is carried independently of the acoustical panels, and heavy items shall be independently supported from the structure rather than relying on the grid alone. Lay-in light fixtures shall be positively attached to the grid with the connections the seismic design requires, and in higher seismic design categories shall additionally be supported by independent slack-safety wires to the structure so that a fixture cannot fall if the grid is displaced. The Contractor shall coordinate the support of every penetrating item so that no item overloads the grid or a single hanger.
+
+## Integration with Light Fixtures, Air Devices, and Sprinklers
+
+The grid layout shall be coordinated with the light fixtures specified under [[sync/lighting-fixtures]], the air distribution devices specified under [[sync/hvac-air-distribution-devices]], and the sprinkler heads specified under [[sync/wet-pipe-fire-sprinkler-systems]] so that each item lands in its intended position relative to the grid and panels. Sprinkler heads that penetrate a panel shall be centered in the panel or located as the sprinkler design and the architectural reflected ceiling plan jointly require, and the escutcheon shall cover the cut neatly; the Contractor shall not field-cut panels for penetrations in positions that conflict with the reflected ceiling plan. Cutouts in panels for downlights, speakers, and devices shall be made with the correct tools to produce clean edges, and panels damaged by miscut penetrations shall be replaced.
+
+## Cutting and Fitting Border Panels
+
+Border and cut panels shall be cut square and clean to fit the grid module at the perimeter and around penetrations, with the cut edge concealed by the perimeter molding or trim. The factory edge shall face the room where a tegular reveal is used so the reveal detail reads consistently; cut tegular edges at borders shall be rabbeted or trimmed to match the field reveal where the architectural detail requires. Cut panels shall not be forced into openings that are too small, which bows the panel, nor left loose in openings that are too large, which leaves gaps.
+
+# Delivery, Storage, and Handling
+
+Suspension components and acoustical panels shall be delivered to the project in the manufacturer's original, undamaged packaging with labels and markings intact. Panels shall be stored flat, indoors, in a dry, climate-controlled space after the building is enclosed and the HVAC is operating, protected from moisture, dust, and physical damage. Panels stored in a damp space or before the building is dry will absorb moisture and warp before they are ever installed; panels stored on an uneven surface or with weight stacked on them will take a permanent bow. Panels and grid that arrive damaged, soiled, or moisture-affected shall be rejected. Installers shall handle panels with clean hands or gloves, because fingerprints and soiling on the panel face cannot be cleaned from many acoustical finishes.
+
+# Warranty
+
+## Manufacturer's Warranty
+
+The suspension system and the acoustical panels shall be warranted by the manufacturer against defects in materials and against sag, warp, or visible deformation under the service conditions for which they were specified, for the manufacturer's standard warranty period. Where humidity sag-resistant panels are specified, the manufacturer shall warrant the panels against sag under the humidity conditions for which they are rated. The grid finish shall be warranted against peeling, flaking, and visible corrosion under normal interior conditions.
+
+```datasheet
+label: Manufacturer Warranty Period
+type: select
+options:
+ - "1 year"
+ - "10 years (typical mineral fiber panel and grid)"
+ - "30 years (premium humidity-resistant systems)"
+default: "10 years (typical mineral fiber panel and grid)"
+```
+
+## Installer's Warranty
+
+The Contractor shall warrant the ceiling installation — including the suspension, hanging, bracing, seismic detailing, perimeter treatment, and panel fit — against defective workmanship for the project warranty period. Workmanship defects include, without limitation, unlevel grid, uneven or unbalanced border panels, panels that do not lie flat in the grid, inadequate or improperly attached hangers and bracing, and seismic details not installed in conformance with ASTM E580 where it applies.
+
+# Spare and Extra Materials
+
+```datasheet
+label: Attic Stock — Acoustical Panels
+type: range
+unit: percent of installed area
+options:
+ min: 1
+ max: 5
+ step: 1
+drawing_ref: true
+default: 2
+```
+
+The Contractor shall deliver to the Owner extra acoustical panels of each type and color installed, equal to the specified percentage of the installed area of that type, for the Owner's future maintenance and replacement. Acoustical panels are routinely damaged, stained by plumbing leaks, and removed for plenum access over the life of a building, and the panel finish and shade are difficult to match exactly with later production; attic stock from the original lot ensures that replacements match the installed ceiling. A 2 percent attic stock is a reasonable default; spaces with frequent plenum access or higher exposure to leaks warrant more. Extra material shall be delivered in the original packaging, clearly labeled with the panel type and color, and stored where the Owner directs.