+---
+title: Mass Timber
+category: Structural
+toc_depth: 3
+description: >
+ When to use: Engineered mass timber structural elements - cross-laminated timber (CLT), structural glued-laminated timber (glulam), nail-laminated timber (NLT), dowel-laminated timber (DLT), and mass plywood panels (MPP) - used as floor, roof, wall, beam, and column members in Type IV-A, IV-B, and IV-C construction.
+ Not intended for: Conventional dimension-lumber framing, sheathing, blocking, and trim (see [[syncs/rough-carpentry]]); steel framing members (see [[syncs/structural-steel-framing]]); or steel connection hardware as a primary system (see [[syncs/structural-steel-connections]]).
+---
+
+# Scope {toc}
+
+## Coverage
+
+### This standard covers the manufacture, fabrication, quality assurance, fire-resistance design, delivery, and installation of engineered mass timber structural elements. Mass timber is a class of large-format engineered wood members built up from smaller laminations, plies, or veneers, valued for prefabricated speed of erection, exposed-wood architecture, carbon sequestration, and an inherent fire-resistance mechanism based on a predictable surface char layer. Elements covered include cross-laminated timber (CLT) panels, structural glued-laminated timber (glulam) beams and columns, nail-laminated timber (NLT) panels, dowel-laminated timber (DLT) panels, and mass plywood panels (MPP). {note}
+
+### The Contractor shall provide all mass timber elements, connection hardware, fasteners, fire protection, and accessories required for a complete and code-compliant structural assembly.
+
+### Steel connectors furnished as part of the mass timber connection system are included in this standard. It does not cover the following, which are specified elsewhere: {note}
+
+- Conventional sawn dimension lumber, sheathing, furring, and non-structural blocking - see [[syncs/rough-carpentry]]
+- Structural steel framing members - see [[syncs/structural-steel-framing]]
+
+### The structural design - member sizing, layup selection, connection design, and lateral-system design - is performed by the Engineer of Record (EOR) and is not superseded by this standard; where this standard and the structural drawings conflict, the structural drawings govern.
+
+# Referenced Standards {toc}
+
+## Applicable Standards
+
+### The following standards are referenced in this section. The edition adopted by the authority having jurisdiction (AHJ) governs where it differs from the edition cited here. {note}
+
+| Standard | Title |
+|----------|-------|
+| ANSI/APA PRG 320 | Standard for Performance-Rated Cross-Laminated Timber |
+| ANSI A190.1 | Standard for Structural Glued Laminated Timber |
+| ANSI/AWC NDS | National Design Specification for Wood Construction (with NDS Supplement: Design Values for Wood Construction) |
+| ANSI/AWC FDS | Fire Design Specification for Wood Construction |
+| AWC SDPWS | Special Design Provisions for Wind and Seismic |
+| IBC | International Building Code (Chapter 6 Type IV construction; Chapter 7 fire-resistance ratings) |
+| ASTM E119 | Standard Test Methods for Fire Tests of Building Construction and Materials |
+| ASTM D2559 | Standard Specification for Adhesives for Bonded Structural Wood Products for Use Under Exterior Exposure Conditions |
+| ASTM E90 / ASTM E413 | Standard Test Method for Measurement of Airborne Sound Attenuation / Classification for Rating Sound Insulation (STC) |
+| ASTM E492 / ASTM E989 | Standard Test Method for Laboratory Measurement of Impact Sound Transmission / Classification for Determination of Impact Insulation Class (IIC) |
+| ASTM E2307 | Standard Test Method for Determining Fire Resistance of Perimeter Fire Barriers |
+| NFPA 285 | Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Non-Load-Bearing Wall Assemblies Containing Combustible Components |
+| TFEC 1 | Standard for Design of Timber Frame Structures and Heavy Timber Construction |
+
+# Construction Type and Fire-Resistance Classification {toc}
+
+## Fire-Resistance Subtypes
+
+### IBC Type IV construction was subdivided in the 2021 IBC into three subtypes - IV-A, IV-B, and IV-C - that differ in required fire-resistance rating (FRR), allowable height, and the percentage of timber that may be left exposed. The applicable IBC edition must be confirmed with the AHJ, because the 2018 IBC does not contain these subtypes: {note}
+
+- Type IV-A requires the primary structural frame to achieve a 3-hour FRR, floors a 2-hour FRR, and roofs a 1.5-hour FRR, with full noncombustible (gypsum) encapsulation of all mass timber.
+- Type IV-B requires a 2-hour primary frame and floor FRR and a 1.5-hour roof FRR, and permits a limited percentage of exposed mass timber as defined by IBC Section 602.4.
+- Type IV-C requires a 1-hour FRR for the primary frame, floors, and roofs, and permits the greatest area of exposed mass timber of the three subtypes.
+
+### The construction-type subtype shall be as designated below, and the required FRR for each element type shall be as shown on the structural and life-safety drawings.
+
+```datasheet
+label: IBC construction type subtype
+type: radio
+options:
+ - Type IV-A (3-hr frame, full encapsulation)
+ - Type IV-B (2-hr frame, partial exposure)
+ - Type IV-C (1-hr frame, greatest exposure)
+default: Type IV-B (2-hr frame, partial exposure)
+```
+
+### Mass timber members shall meet the minimum nominal cross-section dimensions prescribed by IBC Section 602.4 for the designated subtype; a member that satisfies a fire-resistance calculation but is smaller than the prescribed minimum does not qualify as mass timber.
+
+### The fire-resistance design approach for each exposed or partially exposed element shall be one of the methods designated below and shall be coordinated with the EOR before framing shop drawings are issued.
+
+```datasheet
+label: Fire-resistance design approach (exposed members)
+type: radio
+options:
+ - Calculated char per NDS Chapter 16 / AWC FDS
+ - Gypsum encapsulation per AWC FDS / IBC Table 722
+ - Tested assembly per ASTM E119
+default: Calculated char per NDS Chapter 16 / AWC FDS
+```
+
+### The char-calculation method relies on a predictable rate at which the exposed wood surface converts to a protective char layer; below the char and a heat-affected zone, the residual cross-section retains structural capacity. {note}
+
+### Where the calculated char method is used, the nominal char rate shall be taken as the value below unless a member-specific tested rate is substituted with EOR approval.
+
+```datasheet
+label: Nominal char rate (βn)
+type: range
+unit: in/hr
+min: 1.5
+max: 1.8
+step: 0.1
+setpoints: [1.5]
+default: 1.5
+```
+
+### A nominal char rate of 1.5 in/hr applies to glulam and to CLT manufactured to ANSI/APA PRG 320; the residual section is reduced by the char depth plus an additional zero-strength layer per NDS Chapter 16 before checking structural adequacy at the fire limit state. {note}
+
+# Submittals {toc}
+
+## Action Submittals {toc}
+
+### The Contractor shall submit the following action submittals for review before fabrication:
+
+- Product data for each mass timber product, layup, and grade
+- Shop drawings showing member layout, panel and member marks, dimensions, connections, and all penetrations and block-outs
+- Connection design calculations and connector cut sheets with ICC ESR references
+- Fire-resistance design calculations (char calculation or encapsulation layup) signed by the EOR or delegated engineer
+- Erection drawings and sequence
+- Adhesive product data identifying the exposure category (interior dry-service or exterior wet-service)
+
+```datasheet
+label: Action submittals
+type: checkbox
+options:
+ - Product data (products, layups, grades)
+ - Shop drawings (layout, marks, connections, penetrations)
+ - Connection calculations and connector cut sheets
+ - Fire-resistance design calculations
+ - Erection drawings and sequence
+ - Adhesive product data with exposure category
+default: [Product data (products, layups, grades), Shop drawings (layout, marks, connections, penetrations), Connection calculations and connector cut sheets, Fire-resistance design calculations]
+```
+
+### Shop drawings shall show the location and size of every MEP penetration, sleeve, and block-out, because field cutting and notching of structural laminations without EOR approval is prohibited.
+
+### Field cutting or notching of CLT plies, glulam laminations, or panel cross-sections shall not be performed without prior written approval of the EOR.
+
+## Informational Submittals {toc}
+
+### The Contractor shall submit the following informational submittals:
+
+- Third-party certification marks and the inspection agency's qualification statement
+- Mill certificates and grade stamps for laminating lumber, plies, or veneers
+- Adhesive qualification reports per ASTM D2559 where wet-service adhesive is specified
+- Moisture-content test records at delivery
+- Acoustic test reports (STC and IIC) for the specified floor-ceiling assembly
+- Fire-test reports for any listed assemblies relied upon
+
+```datasheet
+label: Informational submittals
+type: checkbox
+options:
+ - Third-party certification and inspection agency qualification
+ - Mill certificates and grade stamps
+ - Adhesive qualification reports (ASTM D2559)
+ - Moisture-content test records at delivery
+ - Acoustic test reports (STC and IIC)
+ - Fire-test reports for listed assemblies
+default: [Third-party certification and inspection agency qualification, Mill certificates and grade stamps, Moisture-content test records at delivery]
+```
+
+## Closeout Submittals {toc}
+
+### The Contractor shall submit the following closeout submittals:
+
+- Final as-built erection drawings reflecting field conditions
+- Manufacturer's warranty
+- Maintenance and finish-care instructions for exposed mass timber surfaces
+- Record of any EOR-approved field modifications
+
+```datasheet
+label: Closeout submittals
+type: checkbox
+options:
+ - As-built erection drawings
+ - Manufacturer's warranty
+ - Maintenance and finish-care instructions
+ - Record of EOR-approved field modifications
+default: [As-built erection drawings, Manufacturer's warranty, Maintenance and finish-care instructions]
+```
+
+# Quality Assurance {toc}
+
+## Product Certification
+
+### Mass timber products manufactured to ANSI A190.1 (glulam) and ANSI/APA PRG 320 (CLT) require third-party inspection and a quality mark; without a named accepted certification body the owner has no mechanism to verify compliance. {note}
+
+### CLT panels shall be manufactured under a third-party quality-assurance program and shall bear a quality mark conforming to ANSI/APA PRG 320.
+
+### Glulam members shall be manufactured under a third-party quality-assurance program and shall bear a quality mark conforming to ANSI A190.1.
+
+### The third-party certification and inspection agency shall be one accepted by the AHJ and designated below.
+
+```datasheet
+label: Third-party certification / inspection agency
+type: select
+options:
+ - APA - The Engineered Wood Association
+ - Timber Products Inspection (TP)
+ - PFS-TECO
+ - Bureau Veritas
+default: APA - The Engineered Wood Association
+```
+
+### The manufacturer shall have a minimum of three years of documented experience producing the specified mass timber product type under the cited product standard.
+
+### The fabricator's shop drawings and connection details shall be prepared or reviewed by a licensed professional engineer.
+
+### A pre-installation conference shall be held before erection begins to review the erection sequence, moisture-protection plan, connection installation, and inspection hold points.
+
+# Environmental and Service Conditions {toc}
+
+## Moisture Management
+
+### Mass timber moves dimensionally with moisture: it shrinks perpendicular-to-grain as it dries toward its in-service equilibrium moisture content (EMC), and it checks or warps if delivered or stored too wet. Controlling moisture is the single most important condition for a durable installation, both at delivery and during construction. Concrete topping or acoustic mat installed over wood above 16% moisture content traps moisture against the wood and risks long-term decay. {note}
+
+### Sawn laminating lumber and glulam members shall not exceed 19% moisture content at the time of delivery.
+
+### Mass timber surfaces shall not exceed the moisture content below before an acoustic mat, topping, or moisture-sensitive finish is installed over them.
+
+```datasheet
+label: Maximum moisture content before topping/finish installation
+type: range
+unit: %
+min: 12
+max: 19
+step: 1
+setpoints: [16, 19]
+default: 16
+```
+
+### The in-service environment shall be designated below; the adhesive exposure category and finish system shall be selected to suit it.
+
+```datasheet
+label: Service exposure condition
+type: radio
+options:
+ - Interior dry-service (MC ≤16%)
+ - Interior intermittently wet during construction
+ - Exterior / wet-service (MC >16%)
+default: Interior dry-service (MC ≤16%)
+```
+
+### Standard interior-use adhesive is not rated for sustained wet-service exposure; exposed exterior or semi-exposed members require an adhesive qualified to ASTM D2559 for exterior conditions. {note}
+
+### The bonding adhesive exposure category shall be as designated below and shall be confirmed against the manufacturer's evaluation report.
+
+```datasheet
+label: Adhesive exposure category
+type: radio
+options:
+ - Interior (dry-service, MC ≤16%)
+ - Exterior (wet-service, MC >16%, ASTM D2559)
+default: Interior (dry-service, MC ≤16%)
+```
+
+### Multi-story mass timber structures accumulate perpendicular-to-grain shrinkage at every floor line; connections, facade attachment, and vertical service runs shall accommodate a cumulative shrinkage allowance of not less than 1/8 in per story.
+
+### Mass timber surfaces left exposed to sky or weather during construction shall be protected from UV degradation and ponded water until permanently enclosed or finished.
+
+# Cross-Laminated Timber (CLT) {toc}
+
+## Panel Properties and Performance Classes
+
+### CLT is a panel built from an odd number of layers (plies) of dimension lumber stacked at right angles and bonded into a single solid panel; the cross-orientation gives the panel two-way capacity and dimensional stability. ANSI/APA PRG 320 defines performance classes: E-rated classes (E1, E2, E3) are governed by the modulus of elasticity and bending strength of the boundary laminations and are selected for structural bending about the major strength axis, while V-rated classes (V1, V2, V3) are visually graded and govern appearance as well as strength. Specifying a performance class without also specifying the layup and ply orientation is a common ordering error; E-rated and V-rated classes are not interchangeable, and a wrong call generates RFIs late in fabrication. {note}
+
+### CLT panels shall conform to ANSI/APA PRG 320 for the performance class, layup, and species combination designated below.
+
+```datasheet
+label: CLT performance class
+type: select
+options:
+ - E1
+ - E2
+ - E3
+ - V1
+ - V2
+ - V3
+default: E1
+```
+
+### The number of plies shall be as designated below and shall correspond to the panel thickness shown on the structural drawings.
+
+```datasheet
+label: CLT layup (plies)
+type: select
+options:
+ - 3-ply
+ - 5-ply
+ - 7-ply
+ - 9-ply
+default: 5-ply
+```
+
+### The CLT panel thickness shall be as designated below; nominal thicknesses correspond to the standard PRG 320 layups for the selected ply count.
+
+```datasheet
+label: CLT panel thickness
+type: range
+unit: in
+min: 3.125
+max: 12.375
+step: 0.125
+setpoints: [4.125, 6.875, 9.625]
+default: 6.875
+```
+
+### The CLT lumber species combination shall be as designated below; species affects allowable stresses, dimensional stability, and regional availability.
+
+```datasheet
+label: CLT species combination
+type: select
+options:
+ - Douglas Fir-Larch
+ - Spruce-Pine-Fir (SPF)
+ - Southern Yellow Pine (SYP)
+ - Hem-Fir
+default: Spruce-Pine-Fir (SPF)
+```
+
+### Panel layout, span direction, and the location of openings shall be as shown on the structural drawings [[drawing: CLT panel layout plan]].
+
+### The exposed-face appearance grade shall be as designated below; appearance grade shall not be applied to concealed (above-ceiling) panels, which adds cost with no benefit.
+
+```datasheet
+label: CLT exposed-face appearance grade
+type: radio
+options:
+ - Industrial (concealed)
+ - Architectural (exposed)
+ - Premium (exposed, premium)
+default: Architectural (exposed)
+```
+
+# Structural Glued-Laminated Timber (Glulam) {toc}
+
+## Member Specification and Appearance Grades
+
+### Glulam is an engineered member made from dimension-lumber laminations bonded face-to-face with the grain running parallel to the member length; it is used for beams, girders, columns, and arches at spans and loads beyond sawn timber. It is specified by a combination symbol that fixes its structural grade, and separately by an appearance grade that fixes its surface quality. The two are independent: 24F-V4 uses visually graded laminations while 24F-E8 uses E-rated laminations, and they carry different allowable stresses and costs. Specifying only an appearance grade (for example, "Architectural") without a combination symbol leaves the structural grade ambiguous and is a frequent source of bid-stage RFIs. {note}
+
+### Glulam members shall conform to ANSI A190.1 for the combination symbol designated below.
+
+```datasheet
+label: Glulam combination symbol
+type: select
+options:
+ - 20F-V3
+ - 24F-V4
+ - 24F-V8
+ - 24F-E8
+ - 26F-V5
+ - 30F-E2
+default: 24F-V4
+```
+
+### Axially loaded glulam columns shall be specified by an axial combination rather than a bending combination, as designated below.
+
+```datasheet
+label: Glulam column axial combination
+type: select
+options:
+ - L1 (Douglas Fir-Larch)
+ - L2 (Douglas Fir-Larch)
+ - 1 (Southern Yellow Pine)
+ - 2 (Southern Yellow Pine)
+default: L1 (Douglas Fir-Larch)
+```
+
+### The glulam species shall be as designated below; Douglas Fir-Larch and Southern Yellow Pine carry different reference design values and shrinkage coefficients and shall not be substituted for one another without a design recheck.
+
+```datasheet
+label: Glulam species
+type: radio
+options:
+ - Douglas Fir-Larch
+ - Southern Yellow Pine (SYP)
+default: Douglas Fir-Larch
+```
+
+### The glulam appearance grade shall be as designated below and shall match the exposure condition in the room-finish schedule.
+
+```datasheet
+label: Glulam appearance grade
+type: select
+options:
+ - Framing
+ - Industrial
+ - Architectural
+ - Premium
+default: Architectural
+```
+
+### Camber shall be provided for horizontal glulam members as designated below to offset dead-load deflection; the camber value shall be confirmed against the EOR's deflection calculations.
+
+```datasheet
+label: Glulam camber (radius of curvature)
+type: select
+options:
+ - No camber
+ - 1600 ft radius
+ - 2000 ft radius
+ - 3500 ft radius
+ - 5000 ft radius
+default: 2000 ft radius
+```
+
+# Other Mass Timber Panel Systems {toc}
+
+## Alternative Panel Types
+
+### Where CLT and glulam do not suit the application, three alternative mass timber panel systems are available: {note}
+
+- Nail-laminated timber (NLT) is built from dimension lumber (2x stock) stacked on edge and nailed together on-face; it is not manufactured to a single national product standard and is designed using NDS sawn-lumber provisions plus diaphragm test data.
+- Dowel-laminated timber (DLT) is built from dimension lumber friction-fit with hardwood dowels and contains no adhesive, which suits projects seeking an adhesive-free panel.
+- Mass plywood panel (MPP) is a cross-laminated veneer panel governed by APA PRP-108 and offers an alternative to CLT where veneer-based layup or thinner plies are advantageous.
+
+### Where a panel system other than CLT or glulam is specified, the panel type shall be as designated below.
+
+```datasheet
+label: Alternative mass timber panel system
+type: radio
+options:
+ - Nail-laminated timber (NLT)
+ - Dowel-laminated timber (DLT)
+ - Mass plywood panel (MPP)
+default: Dowel-laminated timber (DLT)
+```
+
+### NLT and DLT panels used as a structural diaphragm shall be supported by diaphragm shear values established by test or by AWC SDPWS provisions accepted by the EOR.
+
+# Connections {toc}
+
+## Connection System Types
+
+### Mass timber connections range from proprietary concealed steel connectors and self-tapping screws to exposed bearing or notched connections; the choice drives both erection method and the fire-protection requirements of the connection. Concealed steel connectors are protected from fire by the surrounding wood, whereas exposed steel connectors may require supplemental fire protection to meet the connection's required FRR. {note}
+
+### The connection system type shall be as designated below and shall be detailed on the connection shop drawings.
+
+```datasheet
+label: Primary connection system
+type: select
+options:
+ - Concealed proprietary steel connectors
+ - Self-tapping screws (STS)
+ - Concealed knife-plate and dowel
+ - Exposed bearing / notched
+ - Hybrid steel-timber
+default: Concealed proprietary steel connectors
+```
+
+### Self-tapping-screw withdrawal and lateral values vary by manufacturer; specifying a generic "self-tapping screw" without citing an ICC ESR report number and edition leaves the Contractor unable to demonstrate code compliance. {note}
+
+### Self-tapping screws shall be evaluated under a current ICC ESR or designed to NDS provisions, and the governing report number and edition shall be cited on the shop drawings.
+
+### The self-tapping-screw diameter shall be as designated below and shall provide the minimum thread penetration required by the connector evaluation report.
+
+```datasheet
+label: Self-tapping screw diameter
+type: range
+unit: mm
+min: 6
+max: 14
+step: 1
+setpoints: [8, 10, 12]
+default: 10
+```
+
+### Steel connectors, plates, and fasteners furnished as part of the mass timber connection system shall comply with the corrosion-protection and material requirements of [[syncs/structural-steel-connections]].
+
+### Connector hold-down and bearing locations shall be as shown on the connection shop drawings [[drawing: connection detail references]].
+
+### Exposed steel connectors required to contribute to a member's FRR shall be protected by intumescent coating, applied gypsum, or wood cover plates as required by the AWC FDS connection provisions.
+
+# Lateral System Components {toc}
+
+## Diaphragm and Shear Wall Design
+
+### Mass timber buildings resist wind and seismic loads through diaphragms and shear walls; CLT diaphragms and CLT shear walls have design values and detailing rules in AWC SDPWS. {note}
+
+### CLT floor and roof diaphragms shall be designed and detailed to AWC SDPWS, including panel-to-panel spline connections and chord and collector detailing.
+
+### The CLT panel-to-panel edge joint type shall be as designated below.
+
+```datasheet
+label: CLT panel-to-panel edge joint
+type: radio
+options:
+ - Single surface spline
+ - Double surface spline
+ - Half-lap joint
+ - Internal spline
+default: Single surface spline
+```
+
+### Lateral hold-down and shear-transfer hardware at shear walls shall be as shown on the structural drawings [[drawing: shear wall hold-down schedule]].
+
+# Acoustic and Vibration Performance {toc}
+
+## Sound Transmission and Floor Vibration
+
+### Bare mass timber floors transmit airborne and impact sound readily and often fail the vibration frequency thresholds expected of office and residential occupancies; a resilient mat and concrete topping are the usual remedy and must be specified deliberately, not "optional." A floor-ceiling assembly built up with a resilient underlayment mat and a concrete topping over the timber deck raises both STC and IIC ratings and damps floor vibration. {note}
+
+### The floor-ceiling assembly shall achieve the minimum Sound Transmission Class designated below, verified by ASTM E90 testing and ASTM E413 classification.
+
+```datasheet
+label: Minimum floor-ceiling STC rating
+type: range
+unit: STC
+min: 45
+max: 65
+step: 1
+setpoints: [50, 55, 60]
+default: 50
+```
+
+### The floor-ceiling assembly shall achieve the minimum Impact Insulation Class designated below, verified by ASTM E492 testing and ASTM E989 classification.
+
+```datasheet
+label: Minimum floor-ceiling IIC rating
+type: range
+unit: IIC
+min: 45
+max: 65
+step: 1
+setpoints: [50, 55, 60]
+default: 50
+```
+
+### A resilient acoustic underlayment mat shall be installed between the timber deck and the concrete topping where the assembly is required to meet the specified IIC rating.
+
+### The acoustic underlayment mat thickness shall be as designated below.
+
+```datasheet
+label: Acoustic underlayment mat thickness
+type: range
+unit: in
+min: 0.25
+max: 1.0
+step: 0.125
+setpoints: [0.4, 0.5, 0.75]
+default: 0.5
+```
+
+### A concrete topping shall be installed over the timber deck where required for acoustic, fire, or vibration performance; the topping type and thickness shall be as designated below.
+
+```datasheet
+label: Concrete topping
+type: select
+options:
+ - 1.5 in normalweight
+ - 2 in normalweight
+ - 3 in normalweight
+ - 2 in lightweight
+ - 1.5 in gypsum-based underlayment
+default: 2 in normalweight
+```
+
+### Whether the concrete topping acts compositely with the CLT (sharing structural load through shear connectors) or non-compositely (acting only as added dead load) shall be designated below, because composite action requires shear-connector design by the EOR and must be resolved before structural calculations are issued.
+
+```datasheet
+label: Concrete topping structural action
+type: radio
+options:
+ - Non-composite (dead load only)
+ - Composite with CLT (shear-connected)
+default: Non-composite (dead load only)
+```
+
+### Long-span mass timber floors shall satisfy a fundamental frequency check; the minimum acceptable fundamental frequency shall be as designated below for the occupancy served.
+
+```datasheet
+label: Minimum floor fundamental frequency
+type: range
+unit: Hz
+min: 5
+max: 9
+step: 0.5
+setpoints: [5, 8, 9]
+default: 8
+```
+
+### Mass timber floor members shall not exceed a live-load deflection of L/360 or a total-load deflection of L/180 unless a stricter limit is shown on the structural drawings.
+
+# Perimeter and Penetration Firestopping {toc}
+
+## Floor Perimeter Firestopping
+
+### At each floor line, the joint between the mass timber floor and the exterior wall or facade must be firestopped to maintain the floor's fire rating and to resist vertical fire spread up the building perimeter; this is frequently missed in early curtainwall coordination. {note}
+
+### Perimeter joints between the mass timber floor edge and the exterior wall shall be firestopped with a tested perimeter fire-barrier system complying with ASTM E2307 and IBC Section 715.
+
+### Exterior wall assemblies that incorporate combustible cladding or expose mass timber at the exterior face shall comply with NFPA 285 as required by the IBC.
+
+### Through-penetrations of fire-resistance-rated mass timber floors and walls shall be firestopped in accordance with [[syncs/firestopping]].
+
+### Firestop locations and rated-assembly references shall be as shown on the life-safety drawings [[drawing: rated assembly and firestop schedule]].
+
+# Tolerances {toc}
+
+## Manufacturing Tolerances
+
+### Mass timber is prefabricated to tight tolerances so that connectors and panel joints align in the field; the manufacturing tolerances of ANSI A190.1 and ANSI/APA PRG 320 must align with the connection shop drawings. {note}
+
+### Glulam cross-section, length, and camber shall be held within the dimensional tolerances of ANSI A190.1.
+
+### CLT panel length, width, thickness, and squareness shall be held within the dimensional tolerances of ANSI/APA PRG 320.
+
+### CLT panel length shall not deviate from the dimension shown on the shop drawings by more than the tolerance designated below.
+
+```datasheet
+label: CLT panel length tolerance
+type: range
+unit: in
+min: 0.0625
+max: 0.25
+step: 0.0625
+setpoints: [0.125]
+default: 0.125
+```
+
+### CLT panel thickness shall not deviate from the specified thickness by more than ±1/8 in.
+
+### Surface checks, splits, and seasoning effects shall be within the acceptance criteria of the governing product standard for the specified appearance grade.
+
+# Installation {toc}
+
+## Erection and Assembly
+
+### Erection of mass timber shall follow the manufacturer's and EOR's approved erection sequence and shop drawings, including panel and member marks.
+
+### Mass timber elements shall be rigged and lifted using the lifting points and methods shown on the erection drawings to avoid overstressing panels or members during handling.
+
+### Bearing surfaces shall be set on the specified bearing plates, sill seals, and shims; a sill sealer and vapor retarder shall be provided at bearing locations where moisture migration from supporting concrete or masonry is possible.
+
+### The bearing and sill-seal detail at panel and member supports shall be as designated below.
+
+```datasheet
+label: Bearing / sill-seal at supports
+type: select
+options:
+ - Sill seal foam only
+ - Sill seal plus capillary break membrane
+ - Bearing plate with sill seal
+ - Bearing plate with sill seal and vapor retarder
+default: Bearing plate with sill seal
+```
+
+### Self-tapping screws and proprietary connectors shall be installed at the spacing, edge distance, and penetration depth required by the connector evaluation report and shall not be over-driven.
+
+### MEP penetrations shall be made only at the pre-fabricated block-outs and sleeves shown on the shop drawings; field cutting of structural laminations is prohibited without EOR approval.
+
+### Inter-story connections, slotted holes, and facade attachments shall be installed so that the designed perpendicular-to-grain shrinkage allowance is preserved and not shimmed solid.
+
+### Exposed-grade mass timber surfaces shall be protected from damage, staining, and adhesive runout during erection and follow-on trades.
+
+# Field Quality Control {toc}
+
+## Inspection Hold Points
+
+### Moisture content shall be tested at delivery and again before any topping or acoustic mat is installed, and the results shall be recorded against the specified limits as inspection hold points.
+
+### Connections shall be inspected for fastener type, count, spacing, and seating against the approved shop drawings before being concealed.
+
+### Special inspection of mass timber connections and fire-protection encapsulation shall be provided where required by the IBC and the structural drawings.
+
+# Delivery, Storage, and Handling {toc}
+
+## Storage and Protection
+
+### Mass timber is most vulnerable to moisture and mechanical damage between delivery and enclosure; a deliberate storage and cover plan is required, not optional housekeeping. {note}
+
+### Mass timber elements shall be delivered banded, marked, and protected with the manufacturer's factory wrap or an equivalent cover.
+
+### Elements shall be stored off the ground on level dunnage, separated to allow air circulation, and kept covered and ventilated to prevent ponded water and surface staining.
+
+### Elements shall not be delivered or stored uncovered such that the moisture content rises above the specified delivery limit.
+
+### Exposed-grade surfaces shall be handled with edge protection and non-marking slings to prevent crushing, denting, and sling marks.
+
+### Damaged elements, and elements whose moisture content exceeds the specified limit at delivery, shall be rejected and replaced unless remediation is approved in writing by the EOR.
+
+# Warranty {toc}
+
+## Product and Installation Warranty
+
+### The Contractor shall provide the manufacturer's standard written warranty against delamination and manufacturing defects for the mass timber products.
+
+### The warranty period shall be as designated below.
+
+```datasheet
+label: Manufacturer's warranty period
+type: radio
+options:
+ - 1 year
+ - 5 years
+ - 10 years
+ - Limited lifetime
+default: 5 years
+```
+
+### The Contractor shall warrant the installation, including connections and moisture protection performed under this contract, against defects in workmanship for not less than one year from substantial completion.
+
+# Spare Parts and Maintenance {toc}
+
+## Maintenance Instructions and Spares
+
+### The Contractor shall deliver finish-care and maintenance instructions for exposed mass timber surfaces, including approved cleaning agents and re-coating intervals for the specified finish.
+
+### The Contractor shall deliver spare connectors and fasteners of each proprietary type used, in the quantity designated below, for the Owner's future use and repairs.
+
+```datasheet
+label: Spare proprietary connectors / fasteners delivered
+type: radio
+options:
+ - None
+ - 1% of installed quantity
+ - 2% of installed quantity
+ - 5% of installed quantity
+default: 2% of installed quantity
+```
+
+### Touch-up finish material matching the exposed mass timber finish shall be delivered to the Owner in a quantity sufficient for minor field repairs.