Timber Structure Inspection

In accordance with EN 14081 and DIN 4074, structural timber must be strength graded (visually or mechanically) and CE marked. Common grading classes: C16, C24, C30 for softwood. Glued laminated timber (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. Check CE marking and strength class stamp on the timber (e.g. C24)

2. Verify grading class against design 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 grading class limits — knots, splits, wane, bow

- Ungraded timber used for structural purposes

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

- Glulam delamination due to manufacturing defects or moisture exposure

- Timber grading class lower than required by design

In accordance with EN 1995-1-1 Section 8 and DIN EN 1995-1-1/NA, 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 dimensions against design

2. Check minimum edge and end distances

3. Check bolt tightness and washer sizes at bolted connections

4. Inspect metal connectors (joist hangers, angle brackets) for correct size and fixings

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

- Nails or screws too close to edges — splitting risk

- Bolted connections over-tightened — wood crushing

- Missing or incorrectly sized joist hangers

- Connections do not account for moisture movement of timber

In accordance with EN 1995-1-1 Section 2.3.1.3, EN 335, DIN EN 1995-1-1/NA and DIN 68800 (Timber preservation), timber durability depends on the Use Class (UC1-UC5) and the natural durability of the timber species per EN 350. Preservative treatment per EN 351 when natural durability is insufficient. Structural timber in ground contact (UC4) or in water (UC5) requires treatment or naturally durable species (e.g. oak heartwood). In Germany, DIN 68800 governs preventive and remedial timber preservation.

1. Verify that the assigned Use Class of 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. Check detailing for good practice — drainage, ventilation, no moisture traps

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

- Timber in ground contact without treatment or protective barrier

- Poor detailing leads to moisture traps — end grain exposed to weather

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