Wood species
Teak wood
Teak is a hardwood (Tectona grandis). At 12% moisture content it has a Janka hardness of 1,000 lbf (4,448 N) and it weighs about 40 lb/ft³ (643 kg/m³), 3.3 lb (1.52 kg) per board foot.
Key numbers
- Janka hardness, 12% MC
- 1,000 lbf (4,448 N)
- Green: 930 lbf (4,137 N)
- Weight at 12% MC
- 40 lb/ft³ (643 kg/m³)
- 3.3 lb per board foot
- Specific gravity (oven-dry weight)
- 0.55 on green volume
- Shrinkage, green to oven-dry
- 5.8% tangential
- Radial 2.5%, volumetric 7.0%
One source: USDA Forest Products Laboratory, collected from the world literature (its Tables 5-5 and 4-4)
Why: From the USDA Wood Handbook, which collected these values from the world literature; teak's density is worked from its specific gravity with the Handbook's own equations.
How much teak moves
A 12 in wide flatsawn board of teak that goes from 6% to 12% moisture content swells about 0.15 in (about 5/32 in, 3.7 mm). Quartersawn, the same board moves about 0.06 in (about 1/16 in, 1.6 mm). Flatsawn faces move 2.3 times as much as quartersawn ones, because the wood shrinks 5.8% around the growth rings but only 2.5% across them.
Worked from the Wood Handbook's shrinkage values (Table 4-4) with its Eq. 13-4; the Handbook gives no movement coefficients for imported woods. Individual boards vary: the Handbook gives shrinkage a coefficient of variation of about 15% (p. 4-11).
Color, grain and working
- Color
- Yellow-brown to dark golden brown, turning a rich brown in air.
- Grain and texture
- Coarse, uneven texture (ring-porous), usually straight grain, with a distinctly oily feel.
- Working and character
- Excellent dimensional stability and very high natural durability, with strength on par with US oaks. Works with moderate ease, but silica often dulls tools; finishes and glues may need surface pretreatment to bond well.
- Uses
- Boats, furniture, flooring and decorative veneer; tanks, vats and acid-resistant fixtures, because it does not corrode metal in contact.
Adapted in our own words from the Wood Handbook, Chapter 2, p. 2-38.
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE). Values for teak from Wood Handbook Table 5-5b (p. 5-25), which the Handbook says were collected from the world literature, on clear, straight-grained specimens. Knots and cross grain make lumber weaker than these clear samples (Handbook Chapter 5).
| Property | Green | 12% MC |
|---|---|---|
| Bending strength (MOR) | 11,600 psi (80 MPa) | 14,600 psi (101 MPa) |
| Stiffness (MOE) | 1,370,000 psi (9.4 GPa) | 1,550,000 psi (10.7 GPa) |
| Crushing strength (compression parallel to grain) | 5,960 psi (41 MPa) | 8,410 psi (58 MPa) |
| Shear parallel to grain | 1,290 psi (9 MPa) | 1,890 psi (13 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 Tectona grandis as a skin sensitizer.
This is what the named authorities publish, not medical advice.
Compare with
Why these numbers
Why these numbers?
The situation
The Wood Handbook prints 1,000 lbf of side hardness at 12% moisture content for teak, a value it says was collected from the world literature (Table 5-5b, p. 5-25).
One source: USDA Forest Products Laboratory, collected from the world literature (its Tables 5-5 and 4-4) , 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, collected from the world literature (its Tables 5-5 and 4-4) , sources [1]
So
The Handbook gives only the green specific gravity (0.55) for teak, so it is moved to 12% with the volumetric shrinkage of 7% (Eqs. 4-9 and 4-11), then multiplied by water's density and 1.12 (Eq. 4-14).
Arithmetic: exact by definition , sources [1]
The number
About 40 lb/ft³, or 3.3 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources