Wood species
Tamarack wood
Tamarack is a softwood (Larix laricina). At 12% moisture content it has a Janka hardness of 590 lbf (2,624 N) and it weighs about 37 lb/ft³ (594 kg/m³), 3.1 lb (1.4 kg) per board foot.
Also called: eastern larch, hackmatack.
Key numbers
- Janka hardness, 12% MC
- 590 lbf (2,624 N)
- Green: 380 lbf (1,690 N)
- Weight at 12% MC
- 37 lb/ft³ (594 kg/m³)
- 3.1 lb per board foot
- Specific gravity (oven-dry weight)
- 0.53 at 12% MC volume
- 0.49 on green volume
- Shrinkage, green to oven-dry
- 7.4% tangential
- Radial 3.7%, volumetric 13.6%
One source: USDA Forest Products Laboratory, the authority for species properties it measured
Why: Measured by the USDA Forest Products Laboratory; tamarack's density is worked from its specific gravity with the Handbook's own equation.
How much tamarack moves
A 12 in wide flatsawn board of tamarack that goes from 6% to 12% moisture content swells about 0.19 in (about 3/16 in, 4.7 mm). Quartersawn, the same board moves about 0.09 in (about 3/32 in, 2.3 mm). Flatsawn faces move 2 times as much as quartersawn ones, because the wood shrinks 7.4% around the growth rings but only 3.7% across them.
Worked with the Wood Handbook's dimensional change coefficients for tamarack (Table 13-5: 0.00259 tangential, 0.00126 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
- Yellowish-brown to russet heartwood; whitish sapwood, generally under an inch wide.
- Grain and texture
- Coarse, with an abrupt change from earlywood to latewood; no smell or taste.
- Working and character
- Middling in weight and in most mechanical properties.
- Uses
- Framing, tanks, boxes, pallets, posts and poles.
Adapted in our own words from the Wood Handbook, Chapter 2, p. 2-18.
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE). Clear, straight-grained samples of tamarack 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) | 7,200 psi (50 MPa) | 11,600 psi (80 MPa) |
| Stiffness (MOE) | 1,240,000 psi (8.5 GPa) | 1,640,000 psi (11.3 GPa) |
| Crushing strength (compression parallel to grain) | 3,480 psi (24 MPa) | 7,160 psi (49 MPa) |
| Compression perpendicular to grain | 390 psi (3 MPa) | 800 psi (6 MPa) |
| Shear parallel to grain | 860 psi (6 MPa) | 1,280 psi (9 MPa) |
| Tension perpendicular to grain | 260 psi (2 MPa) | 400 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 tamarack 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 × 0.53 × 1.12.
Arithmetic: exact by definition , sources [1]
The number
About 37 lb/ft³, or 3.1 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources