Properties of Douglas Fir

Douglas Fir (Pseudotsuga menziesii) is Canada’s largest conifer and one of the best-known tree species in the world.

Western Larch (Larix occidentalis) is the one conifer species in British Columbia (BC) that loses its needles in the autumn.  It grows in the interior region of BC and has heavy strong wood very comparable to interior Douglas fir.

Douglas fir and western larch are marketed together as Douglas fir.

This species group is used for building and construction purposes because of its high strength, stiffness and durability.  The lumber is usually kiln dried to the customer’s specifications to improve strength, to enhance appearance, to inhibit natural staining, and to increase resistance to decay and insects.

There is a very distinctive difference in color between the spring and summerwood which contributes to a beautiful grain pattern on flat-sawn cuts of lumber.  The wood dries fairly rapidly with minimal change in size or tendency to checking.  Douglas fir has moderately good nail and screw holding properties, glues relatively well, and takes a good paint or stain finish.  Its high strength properties and resistance to corrosion makes it the lumber of choice for heavy timber applications such as warehouse construction, pilings, railway ties, laminated beams, and churches.

It is a massive tree that to heights of 150 – 250 feet (45 – 75m) and diameters of 3 – 8 feet (90 – 245 cm) with some trees occasionally reaching a height of over 300 feet (90m) and 15 feet (455 cm) in diameter.  Douglas Fir trees are shade intolerant and lose their lower branches in dense forest resulting in clear high grade lumber in logs cut from the lower parts of the trunk.

The wood is resinous and often has pitch pockets and secretions of resin on the end and side surfaces.  Freshly cut Douglas fir has a pleasant sweet resinous odor. 

This dense and durable lumber weighs about 34 lbs per cubic foot.