Fir (Douglas)
Strong, stiff softwood and the standard structural framing timber in North America. Good strength-to-weight, but not decay resistant when left exposed.
Properties
- Family
- Wood
- Category
- wood
- Species
- Pseudotsuga menziesii
- Density
- 0.53 g/cm³ · 530 kg/m³
Densityhow fir (douglas) compares
Wood propertiesUSDA clear-wood values at 12% moisture content
- Species measured
- Coast Douglas-fir (Pseudotsuga menziesii)
- Specific gravity
- 0.48
- Janka side hardness
- 710 lbf · 3,158 N
- Modulus of rupture
- 12,400 psi · 85.5 MPa
- Modulus of elasticity
- 1.95 ×10⁶ psi · 13.44 GPa
- Shrinkage, green to oven-dry
- 4.8% radial · 7.6% tangential · 12.4% volumetric
Source: USDA Forest Service, Wood Handbook — Wood as an Engineering Material (FPL-GTR-190, 2010), Table 5–3b, for clear straight-grained specimens at 12% moisture content. The grey figures are converted at 1 lbf = 4.448 N, 1 psi = 6.895 kPa and 1 GPa = 145,038 psi; the inch-pound numbers are the published ones. Specific gravity is oven-dry mass over volume at 12% moisture content, so it sits about 12% below the working density at the top of this page (0.48 × 1.12 ≈ 0.54 g/cm³). The two come from different sampling programmes, so a few species differ by more than that.
Applicationswhere fir (douglas) is normally specified
Appearance & workabilitytrade experience, not measured values
- Origin
- Western North America
- Appearance
- Yellowish to reddish-brown with a strong contrast between earlywood and latewood
- Working
- Strong for its weight and widely used structurally, but the hard latewood bands can splinter and plane unevenly.
Unlike the USDA figures above, these lines are not measurements: they carry no units and no single source. They describe how the timber is generally found to behave rather than what it is guaranteed to do — read them as the consensus of the trade, not as a specification.
Practical notes
- Density is for air-dried stock at about 12% moisture content
- Rated for structural use — check the grade stamp before load-bearing work
- Requires protection outdoors; treat or keep it dry
Lumber sizeswhat fir (douglas) weighs in each nominal size
Lumber size databaseDressed sizes are the same for every species — a 2x4 is 1-1/2 x 3-1/2 in in oak as much as in spruce. What changes is the weight, and that is derived here from fir (douglas)'s density of 0.53 g/cm³.
Tools used on itmatched on the wood family, not on this page
All toolsWhich tools work a material is a property of the family (Wood), not of the individual species — so this list is the same on every wood page, and changes when the tool data changes rather than when this paragraph does.
Used in these projectsbuilds whose bill of materials calls for it
All projectsFrequently asked questionsthe questions this page answers about Fir (Douglas)
How hard is Fir (Douglas)?
Janka hardness is 710 lbf — the force needed to push a steel ball halfway into the wood. Higher is harder; this is the number quoted when a wood is specified for floors, worktops or butcher blocks.
How dense is Fir (Douglas)?
Density is 0.53 g/cm³, and the USDA table gives a specific gravity of 0.48.
How much does Fir (Douglas) move when it dries?
Green to oven-dry it shrinks 12.4% by volume — 4.8% radially and 7.6% tangentially. Movement across the grain is what opens joints, so a species that moves a lot wants room to move.
What is Fir (Douglas) used for?
Typical uses are Structural framing, Beams, Plywood and General construction.
How does Fir (Douglas) work with hand and machine tools?
Strong for its weight and widely used structurally, but the hard latewood bands can splinter and plane unevenly.