Wood species
Red alder wood
Red alder is a hardwood (Alnus rubra). At 12% moisture content it has a Janka hardness of 590 lbf (2,624 N) and it weighs about 29 lb/ft³ (459 kg/m³), 2.4 lb (1.08 kg) per board foot.
Also called: alder.
Key numbers
- Janka hardness, 12% MC
- 590 lbf (2,624 N)
- Green: 440 lbf (1,957 N)
- Weight at 12% MC
- 29 lb/ft³ (459 kg/m³)
- 2.4 lb per board foot
- Specific gravity (oven-dry weight)
- 0.41 at 12% MC volume
- 0.37 on green volume
- Shrinkage, green to oven-dry
- 7.3% tangential
- Radial 4.4%, volumetric 12.6%
One source: USDA Forest Products Laboratory, the authority for species properties it measured
Why: Measured by the USDA Forest Products Laboratory; red alder's density is worked from its specific gravity with the Handbook's own equation.
How much red alder moves
A 12 in wide flatsawn board of red alder that goes from 6% to 12% moisture content swells about 0.18 in (about 3/16 in, 4.7 mm). Quartersawn, the same board moves about 0.11 in (about 3/32 in, 2.8 mm). Flatsawn faces move 1.7 times as much as quartersawn ones, because the wood shrinks 7.3% around the growth rings but only 4.4% across them.
Worked with the Wood Handbook's dimensional change coefficients for red alder (Table 13-5: 0.00256 tangential, 0.00151 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
- Almost white to pale pinkish brown, with no visible line between heartwood and sapwood.
- Working and character
- Moderately light, middling in most strength properties but low in shock resistance, and it shrinks relatively little.
- Uses
- Mostly furniture; also sash and door panel stock and other millwork. It is the main commercial hardwood of Oregon and Washington.
Adapted in our own words from the Wood Handbook, Chapter 2, p. 2-3.
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE). Clear, straight-grained samples of red alder 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) | 6,500 psi (45 MPa) | 9,800 psi (68 MPa) |
| Stiffness (MOE) | 1,170,000 psi (8.1 GPa) | 1,380,000 psi (9.5 GPa) |
| Crushing strength (compression parallel to grain) | 2,960 psi (20 MPa) | 5,820 psi (40 MPa) |
| Compression perpendicular to grain | 250 psi (2 MPa) | 440 psi (3 MPa) |
| Shear parallel to grain | 770 psi (5 MPa) | 1,080 psi (7 MPa) |
| Tension perpendicular to grain | 390 psi (3 MPa) | 420 psi (3 MPa) |
A dash means the Handbook prints no value; none is filled in.
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 red alder at 590 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 × 0.41 × 1.12.
Arithmetic: exact by definition , sources [1]
The number
About 29 lb/ft³, or 2.4 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources