Douglas Fir
Douglas Fir
Pseudotsuga menziesii
Other name: Oregon pine
General description
The country of origin of the Douglas fir is the North West of America. It was introduced 200 years ago in Europe. Properties of the European Douglas Fir (most with a rapid growth) are different from those of its area of origin.
Wood description
The heartwood with its pinkish to dark red colour is clearly demarcated from the yellow sapwood, which has a thickness between 5 and 10 cm. The texture is medium, the timber has a straigght grain.
Douglas Fir may show some resin pockets, sometimes of great dimensions. Softwoods have medium density and good strength properties.
Gluing and sawing properties are good, but due to resin pockets of saw blades may occur. Nailing and screwing properties are good, but pre-boring is necessary and there is a strong tendency to split.
Common uses
The uses of Douglas Fir are similar to those of Larch, mainly for building and construction.
| Physical characteristics | |
|---|---|
| Density (at 12 % moisture content) | 540 kg⁄m3 |
| Total longitudinal shrinkage | 0.3 % |
| Total radial shrinkage | 4.5 % |
| Total tangential shrinkage | 7.5 % |
| Equilibrium moisture content | |
| (20° C⁄ 37 % rel. humidity) | 8.3 % |
| (20° C⁄ 83 % rel. humidity) | 16.1 % |
| Mechanical characteristics | |
| Modulus of elasticity under bending | 12500 N⁄mm2 |
| Modulus of rupture under bending | 95 N⁄mm2 |
| Tension strength | 100 N⁄mm2 |
| Compression strength | 50 N⁄mm2 |
| Brinell hardness perpendicular to the fibres | 20 N⁄mm2 |
| Janka Hardness | 2,5 kN |
| Nail withdrawal strength in N per mm depth and mm diameter | 9.0 N⁄mm2 |
| Natural durability and treatability (according to en 350-2) | |
| Fungi | Class 3 – 4 moderately to poorly durable |
| Dry wood borers | durable |
| Termites | Class S susceptible |
| Treatability | 4 – not permeable |
Natural durability is based on mature heartwood. Sapwood must always be considered as non durable against wood destroying agents.