1 Scope
NOTE This standard governs pre-engineered, metal-plate-connected (MPC) wood roof trusses fabricated in a certified plant and delivered as complete structural assemblies to the project site. (1.1)
NOTE MPC wood trusses are planar structural frames of dimension-lumber chords and webs joined at every panel point by toothed galvanized steel connector plates pressed into both faces of the joint. They replace site-cut rafters and ceiling joists with a factory-engineered assembly whose geometry, member sizes, and plate sizes are determined by a Registered Design Professional (RDP) employed by the component manufacturer. (1.2)
NOTE The scope includes the following truss profiles and configurations. (1.3)
- King-post, queen-post, Fink (W-truss), Howe, and Fan profiles for conventional pitched roofs.
- Scissors and vaulted trusses with a sloped bottom chord for cathedral ceilings.
- Attic (room-in-attic) trusses with a clear interior opening for conditioned attic space.
- Mono (single-slope, lean-to) trusses at additions, shed dormers, and porches.
- Hip and hip-girder systems supplied as a factory-cut hip package with girder, jacks, and fillers.
- Parallel-chord flat and low-slope trusses for flat roofs and mechanical mezzanines.
- Energy-heel (raised-heel) trusses providing full-depth insulation depth at the eave.
- Long-span Howe or Pratt trusses for big-box retail, gymnasiums, and warehouses.
- Multiple-ply girder trusses concentrating loads at hips, valleys, and openings.
NOTE This standard divides engineering responsibility between two parties: the Engineer of Record (EOR) for the building, and the truss designer (the component manufacturer's RDP). The EOR establishes design loads, reactions, bearing conditions, and bracing locations on the contract documents; the truss designer engineers each truss geometry and selects the connector plates. This division is the source of most coordination failures and is reinforced throughout this standard. (1.4)
NOTE The following work is specified elsewhere and is excluded from this standard. (1.5)
1.6Select the governing truss configuration for this project.
Fink (W-truss) common
Howe common
Scissors / vaulted
Attic (room-in-attic)
Mono (single-slope)
Parallel-chord flat / low-slope
Long-span Howe or Pratt
2 Referenced Standards
2.1Materials, design, fabrication, and installation shall comply with the latest adopted edition of each of the following standards unless a specific edition is cited or a different edition is mandated by the authority having jurisdiction.
2.2Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
| Standard |
Title |
| ANSI/TPI 1-2022 |
National Design Standard for Metal Plate Connected Wood Truss Construction |
| BCSI-2025 |
Building Component Safety Information: Guide to Good Practice for Handling, Installing, Restraining & Bracing of Metal Plate Connected Wood Trusses |
| IBC 2024 |
International Building Code, Section 2303.4 (Prefabricated Wood Trusses); Chapter 16 (Loads) |
| IRC 2024 |
International Residential Code, Section R802.10 (Wood Trusses) |
| ANSI/AWC NDS-2024 |
National Design Specification for Wood Construction, with Supplement |
| ASCE/SEI 7-22 |
Minimum Design Loads and Associated Criteria for Buildings and Other Structures |
| ASTM A653/A653M |
Steel Sheet, Zinc-Coated (Galvanized) or Zinc-Iron Alloy-Coated by the Hot-Dip Process |
| ASTM A924/A924M |
General Requirements for Steel Sheet, Metallic-Coated by the Hot-Dip Process |
| DOC PS 2-18 |
Performance Standard for Wood-Based Structural-Use Panels |
| ALSC / NGR |
American Lumber Standard Committee / National Grading Rule for Dimension Lumber |
| AISI S200-20 |
North American Standard for Cold-Formed Steel Framing — General Provisions |
| ICC-ES AC04 |
Acceptance Criteria for Joist Hangers and Similar Devices |
3 Submittals
3.1 Action Submittals
3.1.1The Contractor shall submit the following action submittals for review before fabrication:
- Truss placement (layout) plan showing each truss type, location, orientation, spacing, and bearing.
- Truss design drawings (TDDs) for every distinct truss, each sealed and signed by the truss designer's RDP licensed in the project jurisdiction.
- Girder truss design drawings showing ply count, ply-to-ply fastening pattern, and connector schedule.
- Connector plate data showing gauge, coating designation, and the applicable ICC-ES evaluation report.
- Hanger and uplift tie-down connector schedule with model designations and rated capacities.
- Permanent bracing plan identifying lateral restraint and diagonal bracing locations for web, top-chord, and bottom-chord members.
- Lumber species, grade, and design-value certification for chord and web members.
☑ Truss placement (layout) plan
☑ Sealed truss design drawings (TDDs)
☑ Girder truss design drawings with ply/fastening schedule
☑ Connector plate data and ICC-ES report
☑ Hanger and uplift connector schedule
☑ Permanent bracing plan
☐ Lumber species/grade/design-value certification
3.1.2Truss design drawings shall be reviewed and accepted by the Engineer of Record before fabrication and shall not be treated as for-record-only submittals.
NOTE The truss design drawings are an engineered submittal, not a transmittal. Because the trusses are designed by the component manufacturer's RDP rather than the EOR, the EOR's review confirms that the loads, reactions, bearing, and bracing shown on the TDDs match the design intent of the contract documents. Treating TDDs as for record only is a common defect that leaves the load path unverified. (3.1.3)
3.1.4The Contractor shall coordinate truss profile and interior web geometry with mechanical, electrical, and plumbing routing before submitting truss design drawings for review.
NOTE Attic and scissors trusses have fixed or limited interior geometry. Ducts, flue chases, and equipment that conflict with web members and are discovered after fabrication force costly redesign or prohibited field cutting. Routing coordination belongs in the submittal phase, not the field. (3.1.5)
3.2.1The Contractor shall submit the following informational submittals:
- Plant certification evidence (TPI Quality Criteria program or SBCA Plant Certification).
- Manufacturer's installation, handling, and bracing instructions, including applicable BCSI summary sheets.
- Fire-retardant-treatment (FRT) data with the ICC-ES report establishing plate-embedment design values, where FRT lumber is required.
- Preservative-treatment data, where pressure-preservative-treated lumber is required.
☑ Plant certification evidence
☑ Installation, handling, and bracing instructions (BCSI sheets)
☐ FRT data with plate-embedment ICC-ES report
☐ Preservative-treatment data
3.3 Closeout Submittals
3.3.1The Contractor shall submit the following closeout submittals:
- Record set of as-built truss design drawings reflecting any approved field repairs.
- Engineered repair details for any truss modified, damaged, or repaired in the field.
☑ Record set of as-built truss design drawings
☑ Engineered repair details for field modifications
4 Quality Assurance
4.1 Fabricator Qualifications
4.1.1Trusses shall be fabricated by a plant participating in the TPI Quality Criteria program or the SBCA Plant Certification Program with current certification.
NOTE Plant certification provides third-party verification that connector plates are fully embedded to the depth and tooth-count required by ANSI/TPI 1-2022 Chapter 7. Plate under-embedment is invisible after pressing and silently reduces joint capacity, so independent plant QA is the practical control. (4.1.2)
4.1.3The truss designer shall be a Registered Design Professional licensed in the jurisdiction where the project is located.
4.2 Design Responsibility
4.2.1The Engineer of Record shall provide on the contract documents the design loads, load combinations, truss reactions where governing, required bearing conditions, and permanent bracing locations.
4.2.2The truss designer shall design each truss geometry, member sizes, and connector plates to resist the loads and reactions shown on the contract documents in accordance with ANSI/TPI 1-2022 and ANSI/AWC NDS-2024.
4.2.3Field modification, notching, or drilling of any truss chord or web is prohibited unless authorized in writing by the truss designer or Engineer of Record.
4.2.4Any authorized field modification of a truss chord or web shall be repaired per an engineered detail.
NOTE Truss chords and webs are fully stressed structural members, not nailers or blocking. A field cut that removes section or splits a plate joint reduces capacity at the location of highest demand. Any modification therefore requires engineering review and a supplemental plate or scab repair per ANSI/TPI 1-2022. (4.2.5)
4.3 Source Quality Inspection
4.3.1The Owner reserves the right to inspect fabrication at the plant, including verification of plate embedment, lumber grade marks, and joint gap tolerances.
5 Design Loads and Deflection
5.1 Loading
5.1.1Trusses shall be designed for the dead, roof live, snow, wind, and seismic loads established by the Engineer of Record in accordance with IBC 2024 Chapter 16 (or IRC 2024 for residential occupancies) and ASCE/SEI 7-22.
5.1.2Snow loading shall account for balanced and unbalanced conditions and for drift and sliding-snow surcharge at parapets, step roofs, and adjacent higher roofs where applicable.
5.1.3The design loads shown on the truss design drawings shall match the design loads shown on the contract documents exactly.
NOTE Load mismatch between the contract documents and the TDDs is the single most common and most expensive coordination failure on truss projects. A difference in wind speed, risk category, ground snow load, or dead-load allowance forces TDD re-engineering — often after the trusses are already fabricated. The values must agree before fabrication is released. (5.1.4)
5.1.5Net wind uplift reactions shall be shown on the truss design drawings at every bearing in accordance with IBC 2024 Section 2303.4.
NOTE On longer spans and in high-wind regions the net uplift reaction at a bearing can exceed the gravity reaction. Designing the tie-down to the gravity reaction alone leaves the roof vulnerable to uplift; uplift is a distinct load case that governs the bearing connection. (5.1.6)
5.1.7Specify the governing roof loads for this project.
Per drawings — structural general notes — snow load criteria
Per drawings — structural reactions schedule
5.2 Deflection
5.2.1Live-load deflection of roof trusses supporting a rigid (gypsum) ceiling shall not exceed L/360.
5.2.2Total-load deflection shall not exceed L/240 for trusses supporting a rigid ceiling and L/180 where no rigid ceiling is supported, in accordance with IBC 2024 Table 1604.3.
NOTE Deflection limits protect brittle finishes from cracking and protect drainage slope on low-pitch roofs; the L/360 live-load limit is the residential default because gypsum ceilings crack at larger deflections. Stricter L/480 limits are warranted under tile or stone finishes and under long parallel-chord spans. (5.2.3)
5.2.4Select the live-load deflection limit.
○ L/240 (no rigid ceiling)
● L/360 (gypsum ceiling)
○ L/480 (brittle finish / long span)
○ L/180 (no rigid ceiling)
● L/240 (rigid ceiling)
5.3 Camber
5.3.1Long-span trusses shall be fabricated with upward camber where required by the truss designer to offset dead-load deflection.
NOTE Camber builds an upward curve into the truss so that under sustained dead load the bottom chord settles toward level rather than sagging visibly. Spans up to 40 ft commonly need little or none; spans beyond 60 ft may require 1 to 1.5 in. of camber. Camber is set by the truss designer, not assumed by the installer. (5.3.2)
None (span up to 40 ft)
Standard mill camber
Engineered camber per TDD (long span)
6 Materials
6.1 Lumber
6.1.1Chord and web lumber shall be visually graded or machine-rated dimension lumber bearing the grade mark of an ALSC-accredited agency, with design values from the ANSI/AWC NDS-2024 Supplement.
6.1.2Lumber shall be one of the following species groups: Spruce-Pine-Fir (SPF), Hem-Fir, or Southern Pine, of the grade required by the truss design.
NOTE No. 2 grade Southern Pine or SPF is the typical chord material for residential spans; machine-stress-rated (MSR) or machine-evaluated-lumber (MEL) grades such as 2400f-2.0E are specified for longer spans where higher stiffness and tension capacity are needed. The truss designer selects the grade to meet the engineered demand, so the specification fixes the acceptable species set rather than dictating a single grade. (6.1.3)
6.1.4Lumber moisture content at the time of fabrication shall not exceed 19 percent.
NOTE Plates pressed into lumber wetter than 19 percent can loosen as the wood dries and shrinks, reducing joint capacity. Limiting moisture content at fabrication protects the plate-to-wood connection over the service life of the truss. (6.1.5)
● Spruce-Pine-Fir (SPF)
○ Hem-Fir
○ Southern Pine
No. 2 visually graded
No. 1 visually graded
MSR 2400f-2.0E
MSR 2700f-2.2E
6.2.1Metal connector plates shall be formed from galvanized sheet steel conforming to ASTM A653/A653M (with ASTM A924/A924M general requirements), minimum 20 gauge, with a minimum G60 coating.
6.2.2Connector plates shall carry a current ICC-ES evaluation report establishing their lateral resistance and tooth-withdrawal design values.
6.2.3Connector plates in contact with fire-retardant-treated or preservative-treated lumber, or exposed to weather or wet-service conditions, shall use the heavier coating (G90 or greater) or the stainless-steel plate required by the plate manufacturer's evaluation report for that condition.
NOTE Treatment chemicals and moisture are corrosive to galvanized steel; the standard G60 plate is intended for dry, untreated interior service. Where the plate contacts treated lumber or sees moisture, the manufacturer's evaluation report dictates an upgraded coating or stainless plate, and substituting the standard plate voids the listed capacity. (6.2.4)
● 20 gauge (0.036 in.)
○ 18 gauge (0.048 in.)
○ 16 gauge (0.060 in.)
● G60 galvanized (dry interior)
○ G90 galvanized (treated/exposed)
○ Stainless steel (corrosive/wet)
6.3 Treated Lumber
6.3.1Fire-retardant-treated lumber shall be provided where required for IBC Type III exterior walls and other occupancies mandated by the building code.
6.3.2Plate-embedment design values for connector plates in fire-retardant-treated lumber shall be established by the treatment's ICC-ES evaluation report.
NOTE Generic FRT requirements without a referenced evaluation report are a recurring defect: FRT chemistry reduces the nail-value capacity of connector plates, and only the tested values from the specific treatment's ICC-ES report are valid for design. Specifying "FRT lumber" alone permits an unapproved substitution that the truss capacity does not account for. (6.3.3)
6.3.4Pressure-preservative-treated lumber shall be provided for trusses exposed to weather, in contact with masonry or concrete, or in wet-service conditions, with connector plates upgraded to the coating required for the treatment.
None (dry interior service)
Fire-retardant-treated (FRT) per ICC-ES report
Pressure-preservative-treated
7 Configuration
7.1 Geometry
7.1.1The truss spacing, span, and roof pitch shown on the truss design drawings shall match the truss placement plan and the architectural roof geometry.
NOTE Spacing, span, and pitch are the three parameters that drive every downstream load and member size. Standard residential framing is 24 in. o.c. at a 4:12 to 6:12 pitch over a 28 to 40 ft span; closer spacing or steeper pitch is selected for higher loads, heavier finishes, or architectural ceiling profiles. (7.1.2)
○ 12 in. o.c.
○ 16 in. o.c.
● 24 in. o.c.
7.2 Energy Heel
7.2.1Trusses at insulated eaves shall be provided with a raised (energy) heel where required to maintain the full insulation depth over the exterior wall top plate.
NOTE A standard heel pinches the insulation to almost nothing where the top chord meets the wall, creating a cold edge and condensation risk. The energy heel raises the top-chord/bottom-chord intersection so the specified attic insulation depth continues out over the wall plate; it has been the energy-code-compliant residential default since IECC 2012. (7.2.2)
Standard heel
Energy (raised) heel
7.3 Girder Trusses
7.3.1Girder trusses shall be designed as multiple-ply assemblies with the ply count, ply-to-ply fastening pattern, and connector schedule shown on the truss design drawings.
NOTE A girder truss collects the reactions of the common trusses, hip jacks, or valley framing that bear on it and carries them to the supporting wall or post; its capacity depends on the plies acting together through the specified nailing or bolting. Assuming a ply count rather than specifying it is a frequent field error that produces an under-built girder. (7.3.2)
7.3.3Hangers connecting carried trusses or jacks to girder trusses shall be the rated proprietary connectors shown on the connector schedule, listed under ICC-ES AC04.
8 Bearing and Connections
8.1 Bearing
8.1.1Each truss shall bear over its full specified bearing length on a continuous support capable of resisting the truss reaction without crushing.
8.1.2Truss bearing shall provide a minimum length of 3.5 in. on a wood top plate, 3.5 in. on steel, and 4 in. on masonry or concrete, unless a greater length is shown on the truss design drawings.
NOTE The bearing length controls the perpendicular-to-grain bearing stress in the wall plate. Long-span trusses carry high reactions concentrated on a short heel, and an undersized plate, header, or beam crushes or splits under that reaction. Where the reaction exceeds the plate capacity, a wider plate, a bearing block, or a steel bearing seat is required. (8.1.3)
Bottom-chord bearing on wall plate
Top-chord bearing (hung from beam)
Sloped seat bearing
● 3.5 in. (wood plate / steel)
○ 4 in. (masonry / concrete)
○ Per TDD (high reaction)
8.2 Uplift Tie-Downs
8.2.1A rated uplift tie-down connector shall be provided at every truss bearing to resist the net wind uplift reaction shown on the truss design drawings.
NOTE Uplift connectors create a continuous load path from the truss heel through the top plate and wall studs to the foundation. A break anywhere in that path lets wind peel the roof off; tie-down at the bearing is the first and most critical link, and it is sized to the net uplift reaction, not to a nominal default. (8.2.2)
8.2.3The truss-to-wall connection shall also transfer the lateral and drag (in-plane) loads required by the contract documents.
Twist strap (light uplift)
Hurricane tie (single)
Hurricane tie (double / high uplift)
Embedded strap to wall framing
Engineered holdown per TDD
● Every truss
○ Every truss at exterior bearings; alternate at interior
Per drawings — structural reactions schedule
9 Installation
9.1 Erection and Handling
9.1.1Trusses shall be unloaded, stored, lifted, and erected in accordance with the truss manufacturer's instructions and BCSI-2025.
9.1.2Trusses shall be handled to avoid lateral bending and out-of-plane racking; long-span trusses shall be lifted with a spreader bar or strongback as recommended by BCSI-2025.
NOTE A truss is strong in its own plane and weak out of plane until it is braced. Flat-stacking, edge-dropping, or single-point picking a long truss can buckle a chord or pop a plate before the truss is ever installed. BCSI-2025 gives the picking and storage practices that prevent handling damage. (9.1.3)
9.1.4Trusses damaged in handling or erection shall not be installed until repaired per an engineered detail accepted by the truss designer.
9.2 Temporary Construction Bracing
9.2.1The framing contractor shall provide, install, and maintain all temporary erection bracing required to hold the trusses plumb, straight, and stable until the permanent bracing and sheathing are installed.
NOTE Temporary bracing responsibility belongs to the contractor, not the truss designer. BCSI-2025 is a good-practice guide, not a contract document, so the responsibility for furnishing and installing temporary bracing must be assigned here. The collapse of a partially erected, unbraced truss run during construction is a recurring and preventable safety failure. (9.2.2)
9.2.3Temporary bracing shall remain in place until the roof diaphragm sheathing and all permanent bracing are installed.
● Framing contractor (per BCSI-2025)
○ Erection subcontractor (per BCSI-2025)
9.3 Permanent Bracing
9.3.1Permanent lateral restraint and diagonal bracing shall be installed at the web, top-chord, and bottom-chord locations shown on the truss design drawings and the structural framing plans.
9.3.2Permanent bracing locations shall be shown on the contract structural framing plans as well as on the truss design drawings.
NOTE The truss design drawings identify which individual web members require continuous lateral restraint, but only the EOR's framing plans show how that restraint is itself diagonally braced back into a stable line and tied to the diaphragm. When permanent bracing appears on the TDDs but not on the framing plans, the installer braces individual members without anchoring the bracing system, and the requirement is discovered late as field re-work. (9.3.3)
9.3.4Continuous lateral restraint of compression webs shall be anchored by diagonal bracing or transferred to a braced bay; lateral restraint members shall not be left unbraced.
☑ Top-chord plane (provided by roof sheathing diaphragm)
☐ Bottom-chord continuous lateral restraint
☑ Web member continuous lateral restraint
☑ Diagonal bracing of restraint lines
9.4 Sheathing Interface
9.4.1Roof sheathing attached to the truss top chords shall be wood-based structural-use panels conforming to DOC PS 2-18, installed and fastened under Rough Carpentry. NOTE The roof sheathing diaphragm provides the permanent lateral restraint of the top chords once fastened. Until the sheathing is on, the top chords rely on temporary bracing; the sequencing of sheathing installation is therefore part of the bracing plan, not an independent finishing operation. (9.4.2)
10 Delivery, Storage, and Handling
10.1Trusses shall be delivered banded and tagged with the truss identification matching the truss placement plan.
10.2Trusses shall be stored off the ground on level blocking, supported to prevent lateral bending and excessive bow, and protected from prolonged weather exposure before installation.
10.3Connector plates and treated-lumber trusses shall be kept dry in storage to prevent corrosion of the plates and staining of finishes.
11 Warranty
11.1The fabricator shall warrant that the trusses are free from defects in material and workmanship and are fabricated in conformance with the accepted truss design drawings and ANSI/TPI 1-2022.
NOTE The warranty excludes damage caused by field modification, overloading beyond the design loads, or installation contrary to the manufacturer's instructions and BCSI-2025. (11.2)
● 1 year
○ 2 years
○ 5 years
12 Spare Parts
12.1The fabricator shall furnish engineered repair plate details and any specialty connectors required for anticipated field repairs identified during erection.
NOTE Because field modification of a fabricated truss is prohibited without engineering, the practical "spare part" for a truss roof is a pre-approved repair detail rather than stock components. Keeping repair details and a small reserve of the specified hangers and tie-downs on site avoids a fabrication-plant turnaround when a truss is damaged during construction. (12.2)