Wood species
Eastern hemlock wood
Eastern hemlock is a softwood (Tsuga canadensis). At 12% moisture content it has a Janka hardness of 500 lbf (2,224 N) and it weighs about 28 lb/ft³ (448 kg/m³), 2.3 lb (1.06 kg) per board foot.
Also called: Canadian hemlock, hemlock.
Key numbers
- Janka hardness, 12% MC
- 500 lbf (2,224 N)
- Green: 400 lbf (1,779 N)
- Weight at 12% MC
- 28 lb/ft³ (448 kg/m³)
- 2.3 lb per board foot
- Specific gravity (oven-dry weight)
- 0.40 at 12% MC volume
- 0.38 on green volume
- Shrinkage, green to oven-dry
- 6.8% tangential
- Radial 3.0%, volumetric 9.7%
One source: USDA Forest Products Laboratory, the authority for species properties it measured
Why: Measured by the USDA Forest Products Laboratory; eastern hemlock's density is worked from its specific gravity with the Handbook's own equation.
How much eastern hemlock moves
A 12 in wide flatsawn board of eastern hemlock that goes from 6% to 12% moisture content swells about 0.17 in (about 5/32 in, 4.3 mm). Quartersawn, the same board moves about 0.07 in (about 1/16 in, 1.9 mm). Flatsawn faces move 2.3 times as much as quartersawn ones, because the wood shrinks 6.8% around the growth rings but only 3.0% across them.
Worked with the Wood Handbook's dimensional change coefficients for eastern hemlock (Table 13-5: 0.00237 tangential, 0.00102 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
- Pale brown heartwood with a reddish hue; the sapwood may be lighter.
- Grain and texture
- Coarse and uneven; old trees often have shake.
- Working and character
- Moderately light and hard, fairly low in strength.
- Uses
- Framing, sheathing, subflooring, roof boards, boxes and pallets.
The Handbook reports that the hemlock woolly adelgid, an introduced insect, has led the IUCN to list eastern hemlock as near threatened.
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 eastern hemlock 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) | 6,400 psi (44 MPa) | 8,900 psi (61 MPa) |
| Stiffness (MOE) | 1,070,000 psi (7.4 GPa) | 1,200,000 psi (8.3 GPa) |
| Crushing strength (compression parallel to grain) | 3,080 psi (21 MPa) | 5,410 psi (37 MPa) |
| Compression perpendicular to grain | 360 psi (2 MPa) | 650 psi (4 MPa) |
| Shear parallel to grain | 850 psi (6 MPa) | 1,060 psi (7 MPa) |
| Tension perpendicular to grain | 230 psi (2 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 eastern hemlock at 500 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 × 0.40 × 1.12.
Arithmetic: exact by definition , sources [1]
The number
About 28 lb/ft³, or 2.3 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources