Fir, Douglas

Douglas fir is one of the world’s best-known timber species. Native to the west coast of North America, it is forested extensively in timber plantations throughout Europe, New Zealand and South America – regions where the species has become naturalised. Sawn timber from this species is readily available in Australia.

The heartwood of Douglas fir ranges in colour from yellow through orange to a deep reddish brown. Sapwood is often distinctively paler, occurring in a band from 50 to 75 millimetres in width, depending on the timber’s source. Grain is generally straight, with a pronounced difference in colour between earlywood and latewood that results in a highly distinctive figure on back-sawn surfaces. Texture is often coarse and uneven.

The timber machines and turns well, but planer blades must be kept sharp in order to avoid surface ridging. Care is required with the use of standard fastenings and fittings, as nails may tend to follow the timber’s growth rings. Douglas fir can be satisfactorily bonded using standard glues and procedures. Due to the timber’s high resin content and occasional earlywood–latewood ridging of the dressed product, care is required in selecting timber for finishing applications and in preparation of surfaces for paints and varnishes.

Douglas fir is only moderately durable, and both sapwood and heartwood resist impregnation with preservatives. The timber lacks termite-resistance and sapwood is susceptible to lyctid borer attack.

Douglas fir is commonly found as sawn timber in weather-protected heavy construction applications such as mining timbers, posts and poles. Treated pilings and boards are used in marine structures and for landscaping. Other common applications include general house framing, flooring, lining, fascias, bargeboards and pergolas. It is also used in joinery, turnery, carving and plywood.