Structural Timber Inspection

Per EN 14081, structural timber must be strength graded (visual or machine) and CE marked. Common grades: C16, C24, C30 for softwood. Glulam per EN 14080 (GL24h, GL28h, GL32h). Moisture content at installation must be ≤20% for most applications per EN 1995-1-1 Service Class 1 and 2.

1. Verify timber has CE marking and strength grade stamp (e.g., C24)

2. Check grade matches design specification

3. Measure moisture content with pin meter — must be ≤20% (Service Class 1: ≤12%)

4. For glulam, verify grade marking and check for delamination

5. Inspect for defects exceeding grade limits — knots, splits, wane, bow

- Ungraded timber used for structural purposes

- Moisture content too high at installation — leads to shrinkage and cracking

- Glulam delamination from manufacturing defect or moisture exposure

- Timber grade lower than design requirement

Per EN 1995-1-1 Section 8, timber connections must be designed for the specific fastener type (nails, screws, bolts, dowels, or proprietary connectors). Minimum spacings, edge and end distances per EN 1995-1-1 Table 8.2–8.6. Metal connectors must be corrosion-resistant for the service environment.

1. Verify connection type and fastener size match design

2. Check minimum edge and end distances are maintained

3. Verify bolt tightening and washer sizes for bolted connections

4. Inspect metal connector plates (joist hangers, brackets) — correct size and fixing

5. Check that connections allow for timber movement (shrinkage/swelling)

- Nails or screws too close to edges causing splitting

- Bolted connections over-tightened crushing timber

- Missing or wrong-size joist hangers

- Connections not allowing for timber moisture movement

Per EN 1995-1-1 Section 2.3.1.3 and EN 335, timber durability depends on Use Class (UC1–UC5) and natural durability of the species per EN 350. Preservative treatment per EN 351 where natural durability is insufficient. Structural timber in contact with ground (UC4) or water (UC5) requires treatment or naturally durable species (e.g., oak heartwood).

1. Verify Use Class assigned to each timber element matches its exposure

2. Check timber species is suitable for the Use Class or has been treated

3. Verify preservative treatment certificates where required

4. Inspect for signs of decay, insect attack, or fungal growth

5. Check that detailing prevents moisture traps (good drainage, ventilation)

- Untreated timber used in high-moisture locations (UC3, UC4)

- Timber in contact with ground without treatment or barrier

- Poor detailing trapping moisture — end grain exposed to weather

- Fungal decay in concealed locations (behind cladding, in roof spaces)