Douglas-fir

Category: Softwood
Region: Coast, Interior
Title: Douglas-fir (Pseudotsuga menziesii)

Douglas-fir is a large tree, reaching 85 metres on BC’s coast and 42 metres in the Interior. The oldest trees can be more than 1,500 years old. Douglas-fir is used for building and construction due to its strength, and it is one of the finest timbers for heavy structural purposes, including glulam beams and roof trusses.

Where it grows

There are two varieties of Douglas-fir in BC: coastal and interior. The coastal variety (var. menziesii) is found along the southern mainland coast and across Vancouver Island, except for the very northern tip. The interior variety (var. glauca) occurs throughout southern BC and as far north as Takla Lake near the Yukon border.

Douglas-fir grows in pure, even-aged stands, usually after wildfires; in uneven-aged stands; and in a number of mixed-species stands. The two varieties are found in quite different environments. Interior Douglas-fir can be found in a range of habitats including open forests with pinegrass and moss understory. On the coast, forests are more productive and Douglas-fir grows in mixed stands of western red cedar, hemlock and grand fir.

Did you know?

The common name for Douglas-fir is hyphenated because it is not a true fir. Because of its similarity to other species, it has been called pine, spruce, hemlock and true fir. In 1867, it was given its own genus—Pseudotsuga—which means false hemlock.

Identifiable characteristics

Douglas-fir is a large tree, reaching 85 metres on the West Coast and 42 metres in the Interior. The oldest trees can be more than 1,500 years old. Older trees have a long, branch-free trunk and a short cylindrical crown with a flattened top.

Young Douglas-fir bark is smooth and grey-brown with gummy resin-filled blisters. The bark becomes very thick and deeply grooved with age, growing dark reddish-brown ridges.

Needles are flat with a pointed tip. The upper surface is bright yellowish-green with a single groove down the centre; the lower surface is paler. The needles appear to stand out around the twig. Cones are 5 to 11 centimetres long, turning from green to grey as they mature. Three-pronged flowers are visible between each scale. Seeds are winged at the tip.

Common uses and applications

Due to its strength, Douglas-fir is primarily used for building and construction. It is hard and resistant to abrasion, making it suitable for uses where wear is a factor, such as wharves, trestles, bridge parts, log homes and commercial buildings. It is one of the finest timbers for heavy structural purposes, including glulam beams and roof trusses.

Douglas-fir is a high-quality wood for the manufacturing of sashes, doors and windows. It is also used to produce a wide variety of products including general millwork, flooring, furniture, cabinets, veneer, vats, ships and boats, transmission poles and marine pilings.

Indigenous peoples in BC have many uses for Douglas-fir, including pit cooking fuel, fishing hooks and handles. They also use Douglas-fir boughs for covering the floors of lodges and sweat lodges.

“The Land is a Person”, sculpture by Marianne Nicolson
Photo credit: Barker Manufacturing Inc.

Commercial properties

Douglas-fir has excellent strength properties and is well known for its workability. The wood dries rapidly with small dimensional movement and little tendency to check. It is relatively easy to work, with good machining qualities. It turns, planes and shapes well and can be sanded to a smooth finish. The wood glues moderately easily, has moderate nail and good screw holding ability, and takes a good finish.

The sapwood is narrow in width and light in colour. The heartwood ranges from yellowish to reddish-brown. Earlywood and latewood have a pronounced difference in colour—latewood has darker, more sharply defined bands. This colour difference results in a distinctive grain pattern when flat-sawn. The wood has a fine to medium texture and straight grain and is non-porous.

Coastal Douglas-fir is a much bigger tree than the Interior species, and it is generally lighter in colour with a more uniform texture. Both have the same wood properties, although interior Douglas-fir is less permeable to preservative treatments.

Central City, Surrey
Photo credit: Nic Lehoux

Commercial availability

Douglas-fir is marketed predominantly as Douglas-fir-Larch in structural grades according to National Lumber Grades Authority (NLGA) rules for dimension lumber. Select Structural, #2 and better and stud grades are the most common. Specialty in-house grades and export grades are also available.

Appearance grades are also produced according to NLGA rules. Clears, shop lumber and moulding stock are most common, although there are many potential appearance grades that can be produced.

Douglas-fir lumber is dried according to end-use and customer specifications. Kiln drying inhibits natural staining of the wood, improves its strength and stiffness, enhances its appearance, and increases its resistance to decay and attack by insects.

Did you know?

Europeans discovered the superior qualities of BC timber for ship masts or spars in the late 1700s. British explorer Captain James Cook replaced a mast in BC, likely with coastal Douglas-fir.

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Get acquainted with the most commonly produced and exported lumber grades in boards and structural dimension lumber from BC’s interior softwood species.