Timber Strength Class D40: Properties and Uses
Strength class D40 timber carries a characteristic bending strength of 40 newtons per square millimeter. These are the numbers structural design starts from.
Characteristic bending strength: 40 N/mm²
| Strength class | D40 |
| Characteristic bending strength | 40 N/mm² |
| Mean elastic modulus | 13 GPa |
| Characteristic density | 550 kg per cubic meter |
| Typical source | temperate hardwoods such as oak |
Notes for design and site
D40 is a hardwood class, oak country, with density and embedment strength that transform connection capacity: the same bolt carries far more in D40 than in any softwood. The price is weight, cost, movement as it dries, and tannins that corrode plain steel fasteners, so specify stainless or hot dip galvanized fixings.
Related Calculators and Reference
- Property Library: the full materials reference on this site.
- Bill of Quantities Builder: price the timber package properly.
- Eurocodes at the JRC: the design standards behind these classes.