Wood species
Western red cedar wood
Western red cedar is a softwood (Thuja plicata). At 12% moisture content it has a Janka hardness of 350 lbf (1,557 N) and it weighs about 22 lb/ft³ (358 kg/m³), 1.9 lb (0.85 kg) per board foot.
Also called: western redcedar, canoe cedar, giant arborvitae, Pacific redcedar.
Key numbers
- Janka hardness, 12% MC
- 350 lbf (1,557 N)
- Green: 260 lbf (1,157 N)
- Weight at 12% MC
- 22 lb/ft³ (358 kg/m³)
- 1.9 lb per board foot
- Specific gravity (oven-dry weight)
- 0.32 at 12% MC volume
- 0.31 on green volume
- Shrinkage, green to oven-dry
- 5.0% tangential
- Radial 2.4%, volumetric 6.8%
One source: USDA Forest Products Laboratory, the authority for species properties it measured
Why: Measured by the USDA Forest Products Laboratory; western red cedar's density is worked from its specific gravity with the Handbook's own equation.
How much western red cedar moves
A 12 in wide flatsawn board of western redcedar 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 0.08 in (about 3/32 in, 2 mm). Flatsawn faces move 2.1 times as much as quartersawn ones, because the wood shrinks 5.0% around the growth rings but only 2.4% across them.
Worked with the Wood Handbook's dimensional change coefficients for western redcedar (Table 13-5: 0.00234 tangential, 0.00111 radial per 1% change in moisture content), which hold between 6% and 14%. For this species the Handbook assumes shrinkage starts at 22% moisture content instead of 30%. Individual boards vary: the Handbook gives shrinkage a coefficient of variation of about 15% (p. 4-11).
Color, grain and working
- Color
- Reddish or pinkish brown to dull brown heartwood; narrow, nearly white sapwood.
- Grain and texture
- Generally straight, with a uniform but rather coarse texture.
- Working and character
- Light and moderately soft, weak as a beam or post, with very low shrinkage and very decay-resistant heartwood.
- Uses
- Shingles, siding, decking, interior woodwork, greenhouses, boats, sashes and doors.
Adapted in our own words from the Wood Handbook, Chapter 2, p. 2-17.
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE). Clear, straight-grained samples of western redcedar 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) | 5,200 psi (36 MPa) | 7,500 psi (52 MPa) |
| Stiffness (MOE) | 940,000 psi (6.5 GPa) | 1,110,000 psi (7.7 GPa) |
| Crushing strength (compression parallel to grain) | 2,770 psi (19 MPa) | 4,560 psi (31 MPa) |
| Compression perpendicular to grain | 240 psi (2 MPa) | 460 psi (3 MPa) |
| Shear parallel to grain | 770 psi (5 MPa) | 990 psi (7 MPa) |
| Tension perpendicular to grain | 230 psi (2 MPa) | 220 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.
- Germany's federal list of sensitizing substances (TRGS 907) names Thuja plicata as a sensitizer of the airways and the skin. The ACGIH sets a lower exposure limit for western red cedar dust (0.5 mg/m³) because of asthma, also quoted by OSHA.
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 western redcedar at 350 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 × 0.32 × 1.12.
Arithmetic: exact by definition , sources [1]
The number
About 22 lb/ft³, or 1.9 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources