Wood species
Southern yellow pine wood
Southern yellow pine is a softwood; this page covers the southern pine (major and minor species), led by longleaf pine (Pinus palustris). At 12% moisture content it has a Janka hardness of 870 lbf (3,870 N) and it weighs about 41 lb/ft³ (661 kg/m³), 3.4 lb (1.56 kg) per board foot.
Names and species on this page: southern pine, longleaf pine, loblolly pine, shortleaf pine, slash pine.
Key numbers
- Janka hardness, 12% MC
- 870 lbf (3,870 N)
- Green: 590 lbf (2,624 N)
- Weight at 12% MC
- 41 lb/ft³ (661 kg/m³)
- 3.4 lb per board foot
- Specific gravity (oven-dry weight)
- 0.59 at 12% MC volume
- 0.54 on green volume
- Shrinkage, green to oven-dry
- 7.5% tangential
- Radial 5.1%, volumetric 12.2%
One source: USDA Forest Products Laboratory, the authority for species properties it measured
Why: Measured by the USDA Forest Products Laboratory; southern yellow pine's density is worked from its specific gravity with the Handbook's own equation.
How much southern yellow pine moves
A 12 in wide flatsawn board of longleaf pine that goes from 6% to 12% moisture content swells about 0.18 in (about 3/16 in, 4.5 mm). Quartersawn, the same board moves about 0.1 in (about 3/32 in, 2.5 mm). Flatsawn faces move 1.5 times as much as quartersawn ones, because the wood shrinks 7.5% around the growth rings but only 5.1% across them.
Worked with the Wood Handbook's dimensional change coefficients for longleaf pine (Table 13-5: 0.00248 tangential, 0.00137 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
- Yellowish-white sapwood, wide in second growth, and reddish-brown heartwood.
- Working and character
- Longleaf and slash are heavy, strong, stiff and hard; shortleaf and loblolly are usually somewhat lighter. All shrink a fair amount but are stable when properly dried.
- Uses
- Structural lumber, trusses, beams, joists and piles; treated lumber for decking and posts; structural plywood.
The four major species (longleaf, shortleaf, loblolly, slash) are graded together as Southern Pine; pitch, pond, spruce and Virginia pine are minor species in the same grading rules. The Handbook reports that the IUCN lists longleaf pine as endangered.
Adapted in our own words from the Wood Handbook, Chapter 2, p. 2-15 to 2-16.
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE). Clear, straight-grained samples of longleaf pine 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) | 8,500 psi (59 MPa) | 14,500 psi (100 MPa) |
| Stiffness (MOE) | 1,590,000 psi (11 GPa) | 1,980,000 psi (13.7 GPa) |
| Crushing strength (compression parallel to grain) | 4,320 psi (30 MPa) | 8,470 psi (58 MPa) |
| Compression perpendicular to grain | 480 psi (3 MPa) | 960 psi (7 MPa) |
| Shear parallel to grain | 1,040 psi (7 MPa) | 1,510 psi (10 MPa) |
| Tension perpendicular to grain | 330 psi (2 MPa) | 470 psi (3 MPa) |
A dash means the Handbook prints no value; none is filled in.
The southern pine (major and minor species)
The Handbook tests each species separately; they are sold together as southern yellow pine. Across the 5 species measured, Janka hardness at 12% runs from 660 to 870 lbf.
| Species | Janka, 12% MC | Weight, 12% MC | Tangential shrinkage |
|---|---|---|---|
| Longleaf pinePinus palustris | 870 lbf | 41 lb/ft³ | 7.5% |
| Loblolly pinePinus taeda | 690 lbf | 36 lb/ft³ | 7.4% |
| Shortleaf pinePinus echinata | 690 lbf | 36 lb/ft³ | 7.7% |
| Slash pinePinus elliottii | — | 41 lb/ft³ | 7.6% |
| Pitch pinePinus rigida | — | 36 lb/ft³ | 7.1% |
| Pond pinePinus serotina | — | 39 lb/ft³ | 7.1% |
| Spruce pinePinus glabra | 660 lbf | 31 lb/ft³ | — |
| Virginia pinePinus virginiana | 740 lbf | 34 lb/ft³ | 7.2% |
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 longleaf pine at 870 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 × 0.59 × 1.12.
Arithmetic: exact by definition , sources [1]
The number
About 41 lb/ft³, or 3.4 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources