Wood species
Post oak wood
Post oak is a hardwood (Quercus stellata). At 12% moisture content it has a Janka hardness of 1,360 lbf (6,050 N) and it weighs about 47 lb/ft³ (750 kg/m³), 3.9 lb (1.77 kg) per board foot.
Also called: Quercus stellata.
Key numbers
- Janka hardness, 12% MC
- 1,360 lbf (6,050 N)
- Green: 1,130 lbf (5,026 N)
- Weight at 12% MC
- 47 lb/ft³ (750 kg/m³)
- 3.9 lb per board foot
- Specific gravity (oven-dry weight)
- 0.67 at 12% MC volume
- 0.60 on green volume
- Shrinkage, green to oven-dry
- 9.8% tangential
- Radial 5.4%, volumetric 16.2%
One source: USDA Forest Products Laboratory, the authority for species properties it measured
Why: Measured by the USDA Forest Products Laboratory; post oak's density is worked from its specific gravity with the Handbook's own equation.
How much post oak moves
A 12 in wide flatsawn board of post oak that goes from 6% to 12% moisture content swells about 0.26 in (about 1/4 in, 6.5 mm). Quartersawn, the same board moves about 0.14 in (about 1/8 in, 3.4 mm). Flatsawn faces move 1.8 times as much as quartersawn ones, because the wood shrinks 9.8% around the growth rings but only 5.4% across them.
Worked from the Wood Handbook's shrinkage values (Table 4-3) with its Eq. 13-4. Individual boards vary: the Handbook gives shrinkage a coefficient of variation of about 15% (p. 4-11).
Color, grain and working
- Color
- Generally grayish brown heartwood; nearly white sapwood about 1 to 2 in. wide.
- Grain and texture
- Heartwood pores usually plugged with tyloses; broad, conspicuous rays on quartersawn faces.
- Working and character
- Somewhat heavier than red oak, and its heartwood has good decay resistance.
- Uses
- White oak goes into tight barrels, boat planking and bent parts, furniture, flooring, doors and millwork.
The Handbook describes the white oaks as a group; this page gives this oak’s own tested figures.
Adapted in our own words from the Wood Handbook, Chapter 2, p. 2-9.
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE). Clear, straight-grained samples of post oak 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) | 8,100 psi (56 MPa) | 13,200 psi (91 MPa) |
| Stiffness (MOE) | 1,090,000 psi (7.5 GPa) | 1,510,000 psi (10.4 GPa) |
| Crushing strength (compression parallel to grain) | 3,480 psi (24 MPa) | 6,600 psi (46 MPa) |
| Compression perpendicular to grain | 860 psi (6 MPa) | 1,430 psi (10 MPa) |
| Shear parallel to grain | 1,280 psi (9 MPa) | 1,840 psi (13 MPa) |
| Tension perpendicular to grain | 790 psi (5 MPa) | 780 psi (5 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
Buying and finishing post oak
Work it out for your project
- Rank woods for furniture with the species picker
Weigh post oak against other woods on hardness, weight, movement and color, every figure from the Wood Handbook.
- Plan a finish for furniture in post oak
The finishes whose makers name that use, and a dated coat schedule from each product’s own sheet.
Why these numbers
Why these numbers?
The situation
The USDA Forest Products Laboratory measured post oak at 1,360 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 × 0.67 × 1.12.
Arithmetic: exact by definition , sources [1]
The number
About 47 lb/ft³, or 3.9 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources