Wood species
Fir wood
Fir is a softwood; this page covers the true firs (eastern and western), led by white fir (Abies concolor). At 12% moisture content it has a Janka hardness of 480 lbf (2,135 N) and it weighs about 27 lb/ft³ (437 kg/m³), 2.3 lb (1.03 kg) per board foot.
Names and species on this page: true fir, white fir, balsam fir, grand fir, noble fir, Pacific silver fir.
Key numbers
- Janka hardness, 12% MC
- 480 lbf (2,135 N)
- Green: 340 lbf (1,512 N)
- Weight at 12% MC
- 27 lb/ft³ (437 kg/m³)
- 2.3 lb per board foot
- Specific gravity (oven-dry weight)
- 0.39 at 12% MC volume
- 0.37 on green volume
- Shrinkage, green to oven-dry
- 7.0% tangential
- Radial 3.3%, volumetric 9.8%
One source: USDA Forest Products Laboratory, the authority for species properties it measured
Why: Measured by the USDA Forest Products Laboratory; fir's density is worked from its specific gravity with the Handbook's own equation.
How much fir moves
A 12 in wide flatsawn board of white fir that goes from 6% to 12% moisture content swells about 0.18 in (about 3/16 in, 4.5 mm). Quartersawn, the same board moves about 0.08 in (about 3/32 in, 2 mm). Flatsawn faces move 2.1 times as much as quartersawn ones, because the wood shrinks 7.0% around the growth rings but only 3.3% across them.
Worked with the Wood Handbook's dimensional change coefficients for white fir (Table 13-5: 0.00245 tangential, 0.00112 radial per 1% change in moisture content), which hold between 6% and 14%. Individual boards vary: the Handbook gives shrinkage a coefficient of variation of about 15% (p. 4-11).
Color, grain and working
- Color
- Creamy white to pale brown; heartwood and sapwood are generally indistinguishable.
- Grain and texture
- The true firs can’t be told apart by the wood alone; western species are sold together as “white fir”.
- Working and character
- Light and soft. Balsam fir is low in strength; the western firs except subalpine are somewhat stronger. Shrinkage is low to fairly high.
- Uses
- Framing, subflooring, sheathing, boxes, millwork, sashes and doors; high-grade noble fir for interior woodwork and molding.
Adapted in our own words from the Wood Handbook, Chapter 2, p. 2-12.
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE). Clear, straight-grained samples of white fir tested by the Forest Products Laboratory (Wood Handbook Table 5-3b). Knots and cross grain make lumber weaker than these clear samples (Handbook Chapter 5).
| Property | Green | 12% MC |
|---|---|---|
| Bending strength (MOR) | 5,900 psi (41 MPa) | 9,800 psi (68 MPa) |
| Stiffness (MOE) | 1,160,000 psi (8 GPa) | 1,500,000 psi (10.3 GPa) |
| Crushing strength (compression parallel to grain) | 2,900 psi (20 MPa) | 5,800 psi (40 MPa) |
| Compression perpendicular to grain | 280 psi (2 MPa) | 530 psi (4 MPa) |
| Shear parallel to grain | 760 psi (5 MPa) | 1,100 psi (8 MPa) |
| Tension perpendicular to grain | 300 psi (2 MPa) | 300 psi (2 MPa) |
A dash means the Handbook prints no value; none is filled in.
The true firs (eastern and western)
The Handbook tests each species separately; they are sold together as fir. Across the 7 species measured, Janka hardness at 12% runs from 350 to 500 lbf.
| Species | Janka, 12% MC | Weight, 12% MC | Tangential shrinkage |
|---|---|---|---|
| White firAbies concolor | 480 lbf | 27 lb/ft³ | 7.0% |
| Balsam firAbies balsamea | 380 lbf | 24 lb/ft³ | 6.9% |
| Grand firAbies grandis | 490 lbf | 26 lb/ft³ | 7.5% |
| Noble firAbies procera | 410 lbf | 27 lb/ft³ | 8.3% |
| Pacific silver firAbies amabilis | 430 lbf | 30 lb/ft³ | 9.2% |
| California red firAbies magnifica | 500 lbf | 27 lb/ft³ | 7.9% |
| Subalpine firAbies lasiocarpa | 350 lbf | 22 lb/ft³ | 7.4% |
Dust and health
- Wood dust is classed as carcinogenic to humans (Group 1) by the International Agency for Research on Cancer, chiefly for cancers of the nose and sinuses.
- NIOSH recommends keeping wood dust exposure to 1 mg/m³ of total dust, as quoted in OSHA's sawmill guidance.
This is what the named authorities publish, not medical advice.
Compare with
Why these numbers
Why these numbers?
The situation
The USDA Forest Products Laboratory measured white fir at 480 lbf of side hardness at 12% moisture content, on clear, straight-grained samples (Wood Handbook Table 5-3b).
One source: USDA Forest Products Laboratory, the authority for species properties it measured , sources [1]
What that means
Side hardness (Janka) is the load needed to press a 0.444 in (11.28 mm) steel ball halfway into the wood across the grain; a higher number dents less (Handbook p. 5-5).
One source: USDA Forest Products Laboratory, the authority for species properties it measured , sources [1]
So
Density at 12% is water's density × specific gravity × (1 + 0.12) (Handbook Eq. 4-14): 62.43 × 0.39 × 1.12.
Arithmetic: exact by definition , sources [1]
The number
About 27 lb/ft³, or 2.3 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources