Structural Timber Inspection

Per CSA O86 Clause 5 and CSA O141, all structural lumber must be grade-stamped by a certified grading agency accredited by the Canadian Lumber Standards Accreditation Board (CLSAB). Lumber species and grade must match the design drawings (e.g., SPF No. 1/No. 2, D.Fir-L Select Structural). Glued-laminated timber (glulam) must conform to CSA O122 and bear the appropriate certification mark.

1. Verify all structural lumber bears a grade stamp from a CLSAB-accredited grading agency showing species, grade, and moisture content designation

2. Confirm lumber species and grade match the structural design drawings and CSA O86 specified strength values

3. Check that glulam beams and columns bear CSA O122 certification marks with stress grade identification

4. Measure moisture content using a calibrated pin-type moisture metre and confirm it is within acceptable limits (typically 19% or less for framing lumber)

5. Inspect lumber for excessive wane, splits, checks, and decay that exceed grade limits

- Unstamped or incorrectly graded lumber used for structural members

- Lumber delivered at elevated moisture content leading to shrinkage, warping, and fastener loosening after installation

- Glulam members without CSA O122 certification marks indicating unverified manufacturing

- Excessive defects (knots, splits) beyond grade limits reducing member capacity

Per NBC Part 9 (Sections 9.23 and 9.4) and CSA O86, structural framing must conform to design drawings for member size, spacing, and span. Joists, rafters, and studs must meet the span tables in NBC Part 9 or be designed per CSA O86 engineering calculations. Bearing points must provide minimum 38 mm bearing length per NBC 9.23.5.

1. Verify joist, rafter, and stud sizes and spacing match design drawings or NBC Part 9 span tables

2. Confirm member spans do not exceed maximum allowable spans for the species, grade, and loading conditions

3. Check that all bearing points provide minimum 38 mm bearing length per NBC 9.23.5

4. Verify doubled or built-up members are properly nailed or bolted together per NBC 9.23.4

5. Confirm headers over openings are sized per NBC Table 9.23.12 or engineered design

- Joist or rafter spacing exceeding design requirements (e.g., 600 mm o.c. used where 400 mm o.c. is required)

- Member spans exceeding NBC span table limits for the species and grade

- Insufficient bearing at supports causing crushing of wood fibres

- Headers undersized for the tributary load above openings

Per CSA O86 Clause 12 and NBC 9.23.3, timber connections must be designed and installed to transfer the required loads. Nailed connections must use the correct nail size, quantity, and spacing per CSA O86 or NBC nailing schedules. Engineered connectors (joist hangers, hurricane ties, hold-downs) must be installed per manufacturer's evaluation reports. Bolted connections must meet CSA O86 minimum end, edge, and spacing distances.

1. Verify nailing patterns match NBC 9.23.3 nailing schedules or engineered design requirements

2. Confirm engineered connectors (joist hangers, beam seats, hold-downs) are the correct model and installed with specified fasteners per manufacturer's instructions

3. Check bolt sizes, spacing, end distance, and edge distance against CSA O86 Clause 12.4 minimum requirements

4. Verify all connectors at critical load paths (shear walls, drag struts, hold-downs) are properly installed

5. Confirm lag screws and timber screws are pre-drilled per CSA O86 requirements to prevent splitting

- Joist hangers installed with incorrect nails (e.g., roofing nails instead of specified joist hanger nails)

- Missing hold-downs or straps at shear wall overturning connections

- Bolts installed too close to member ends or edges causing splitting

- Nails hand-driven and missing framing members at sheathing-to-framing connections

Per NBC Part 9 (Section 9.23.13) and CSA O86, buildings must be braced to resist lateral wind and seismic forces. Shear walls must use specified sheathing (plywood or OSB conforming to CSA O325) with correct nailing patterns per CSA O86 Clause 11 or NBC 9.23.13. Hold-downs and anchor bolts must be provided at shear wall ends to resist overturning forces.

1. Verify shear wall locations and lengths match the design drawings and bracing requirements per NBC 9.23.13

2. Confirm sheathing is CSA O325 rated, correct thickness, and installed with the strength axis perpendicular to framing

3. Check nailing pattern at shear wall panels: nail size, spacing at edges and field per CSA O86 or NBC requirements

4. Verify hold-downs and anchor bolts are installed at shear wall ends and properly connected to the foundation

5. Confirm blocking is provided at all sheathing panel edges per design requirements

- Shear wall nailing too widely spaced reducing lateral resistance capacity

- Hold-downs missing or not tightened at shear wall overturning connections

- Sheathing panels not staggered at corners creating weak joints

- Openings cut into designated shear walls without engineering approval

Per CSA O86 and NBC Part 4, engineered wood products including I-joists, laminated veneer lumber (LVL), parallel strand lumber (PSL), and cross-laminated timber (CLT) must be installed per the manufacturer's design guide and evaluation reports. These products must not be field-modified (notched, drilled, or cut) except as permitted by the manufacturer. CLT must conform to ANSI/APA PRG 320 and CSA O86 Clause 8.

1. Verify engineered wood products are the correct type, depth, and series as specified in the design documents

2. Confirm products bear the appropriate certification marks (e.g., CCMC evaluation number) and are installed per manufacturer's instructions

3. Check that I-joists are not notched, cut, or drilled outside the manufacturer's permitted zones

4. Verify web stiffeners and blocking are installed at I-joist bearing points and load concentration points per manufacturer's requirements

5. Confirm CLT panels are installed with correct orientation and connection details per CSA O86 Clause 8

- I-joist webs cut or notched in prohibited zones causing structural failure

- Web stiffeners missing at bearing points of I-joists leading to web buckling

- LVL or PSL members installed with incorrect orientation (flat instead of on edge)

- Engineered wood products stored improperly on site, exposed to sustained moisture

Per NBC 9.23.2 and CSA O80 series, wood in contact with concrete, masonry, or ground must be preservative-treated or naturally durable. Permanent wood foundations must use lumber and plywood treated per CSA S406 and CSA O80. Sill plates must be pressure-treated and separated from concrete with a moisture barrier per NBC 9.23.6. Ventilation of enclosed wood spaces must meet NBC 9.19 requirements.

1. Verify all sill plates and wood in contact with concrete or masonry are pressure-treated per CSA O80 and bear treatment stamps

2. Confirm treated wood retention levels match the specified end-use category per CSA O80 (e.g., UC4A for ground contact)

3. Check that a moisture barrier (sill gasket or polyethylene) is installed between sill plates and concrete foundation per NBC 9.23.6

4. Verify adequate crawl space ventilation per NBC 9.19 or vapour barrier coverage over exposed soil

5. Confirm field-cut ends and drill holes in treated wood are re-treated with approved preservative per CSA O80

- Untreated lumber used in ground-contact or concrete-contact applications

- Sill gasket omitted allowing moisture wicking from foundation into framing

- Field cuts on treated wood not re-treated allowing decay at cut ends

- Inadequate crawl space ventilation leading to elevated moisture and wood decay

Per NBC Part 3, wood-frame construction must meet the fire resistance rating required for the building's occupancy and height. Fire stops must be installed in concealed spaces per NBC 3.1.11 and 9.10.16. Heavy timber construction must meet NBC 3.2.2.8 minimum member dimensions. Mass timber (CLT) assemblies must achieve fire resistance ratings through char calculations per CSA O86 Annex B or ULC-listed assemblies.

1. Verify fire stop materials are installed at all required locations per NBC 9.10.16 (floor/ceiling, wall, and roof concealed spaces)

2. Confirm fire stops are properly sealed around penetrations (pipes, ducts, wiring) using listed firestop systems

3. Check that heavy timber members meet minimum dimensions per NBC 3.2.2.8 (e.g., 140 mm beams, 89 mm decking)

4. Verify gypsum board fire protection is installed per ULC-listed assembly details with correct type, thickness, and fastening

5. Confirm mass timber (CLT) fire resistance is validated through char rate calculations per CSA O86 Annex B

- Fire stops missing in concealed stud and joist spaces at floor and wall intersections

- Penetrations through fire-rated assemblies not sealed with listed firestop systems

- Gypsum board not properly fastened or wrong type used in fire-rated assemblies

- Heavy timber members undersized for the fire resistance rating claimed