Timber Structure Inspection

In accordance with EN 14081, structural timber must be strength graded (visually or mechanically) and CE marked. Common classes: 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. CTE DB SE-M supplements these requirements.

1. Check timber for CE marking and strength class stamp (e.g. C24)

2. Verify class matches project specification

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

4. For glulam, check class marking and inspect for delamination

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

- Ungraded timber used for structural purposes

- Moisture content too high at installation — causes shrinkage and cracking

- Glulam delamination due to manufacturing defect or moisture exposure

- Timber class lower than required by design

In accordance with 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 Tables 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 respected

3. Verify bolt tightness and washer sizes at bolted connections

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

5. Ensure connections allow timber movement (shrinkage/swelling)

- Nails or screws too close to edges causing splitting

- Bolted connections over-tightened crushing the timber

- Joist hangers missing or incorrectly sized

- Connections not allowing moisture-related timber movement

In accordance with EN 1995-1-1 Section 2.3.1.3 and EN 335, timber durability depends on the Use Class (UC1-UC5) and the natural durability of the species per EN 350. Preservative treatment per EN 351 is required when natural durability is insufficient. Structural timber in ground contact (UC4) or water (UC5) requires treatment or naturally durable species (e.g. oak heartwood). CTE DB SE-M Section 3 establishes specific durability requirements.

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

2. Check that the 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. Ensure detailing avoids moisture traps (good drainage, ventilation)

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

- Timber in ground contact without treatment or barrier

- Poor detailing retaining moisture — end grain exposed to weather

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