Wood species
Ash wood
Ash is a hardwood; this page covers the ash (white and black ash groups), led by white ash (Fraxinus americana). At 12% moisture content it has a Janka hardness of 1,320 lbf (5,872 N) and it weighs about 42 lb/ft³ (672 kg/m³), 3.5 lb (1.59 kg) per board foot.
Names and species on this page: white ash, American white ash, green ash, black ash.
Key numbers
- Janka hardness, 12% MC
- 1,320 lbf (5,872 N)
- Green: 960 lbf (4,270 N)
- Weight at 12% MC
- 42 lb/ft³ (672 kg/m³)
- 3.5 lb per board foot
- Specific gravity (oven-dry weight)
- 0.60 at 12% MC volume
- 0.55 on green volume
- Shrinkage, green to oven-dry
- 7.8% tangential
- Radial 4.9%, volumetric 13.3%
One source: USDA Forest Products Laboratory, the authority for species properties it measured
Why: Measured by the USDA Forest Products Laboratory; ash's density is worked from its specific gravity with the Handbook's own equation.
How much ash moves
A 12 in wide flatsawn board of white ash that goes from 6% to 12% moisture content swells about 0.2 in (about 3/16 in, 5 mm). Quartersawn, the same board moves about 0.12 in (about 1/8 in, 3.1 mm). Flatsawn faces move 1.6 times as much as quartersawn ones, because the wood shrinks 7.8% around the growth rings but only 4.9% across them.
Worked with the Wood Handbook's dimensional change coefficients for white ash (Table 13-5: 0.00274 tangential, 0.00169 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
- Brown heartwood and light, nearly white sapwood. Black ash heartwood is a darker brown than white ash.
- Working and character
- White ash, especially from second-growth trees, is heavy, strong, hard and stiff with high shock resistance. The black ash group is noticeably lighter.
- Uses
- Tool handles, oars, baseball bats and other sporting goods; also cabinets, furniture, flooring, millwork and decorative veneer.
The Handbook reports that the IUCN lists white, green, blue and black ash as critically endangered because of the emerald ash borer, and that infested trees, living and dead, are being harvested widely.
Adapted in our own words from the Wood Handbook, Chapter 2, p. 2-4.
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE). Clear, straight-grained samples of white ash 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) | 9,500 psi (66 MPa) | 15,400 psi (106 MPa) |
| Stiffness (MOE) | 1,440,000 psi (9.9 GPa) | 1,740,000 psi (12 GPa) |
| Crushing strength (compression parallel to grain) | 3,990 psi (28 MPa) | 7,410 psi (51 MPa) |
| Compression perpendicular to grain | 670 psi (5 MPa) | 1,160 psi (8 MPa) |
| Shear parallel to grain | 1,350 psi (9 MPa) | 1,910 psi (13 MPa) |
| Tension perpendicular to grain | 590 psi (4 MPa) | 940 psi (6 MPa) |
A dash means the Handbook prints no value; none is filled in.
The ash (white and black ash groups)
The Handbook tests each species separately; they are sold together as ash. Across the 4 species measured, Janka hardness at 12% runs from 850 to 1,320 lbf.
| Species | Janka, 12% MC | Weight, 12% MC | Tangential shrinkage |
|---|---|---|---|
| White ashFraxinus americana | 1,320 lbf | 42 lb/ft³ | 7.8% |
| Green ashFraxinus pennsylvanica | 1,200 lbf | 39 lb/ft³ | 7.1% |
| Blue ashFraxinus quadrangulata | — | 41 lb/ft³ | 6.5% |
| Oregon ashFraxinus latifolia | 1,160 lbf | 38 lb/ft³ | 8.1% |
| Black ashFraxinus nigra | 850 lbf | 34 lb/ft³ | 7.8% |
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 ash at 1,320 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 × 0.60 × 1.12.
Arithmetic: exact by definition , sources [1]
The number
About 42 lb/ft³, or 3.5 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources