Paper birch
Betula papyrifera
Paper birch measures 910 lbf on the Janka scale, 29% softer than northern red oak.
- Of the three birches in the handbook, none is softer or lighter, and none bends more easily or shrinks less across the face.
- Only nine of the 155 woods have a T/R ratio closer to 1.
- Drying hardens it more than most: from 560 lbf green, it gains 62% by 12% moisture, where the median wood gains 31%.
- Ocote pine has exactly the same Janka figure.
U.S. hardwoodsU.S. softwoodsImported woodsNorthern red oak
Six measures
Paper birchU.S. hardwoods medianOther woods
Cupping tendency
1.3710th lowest of 15527% below the U.S. hardwoods median1.092.90Shrinkage across the face
8.6%radial 6.3%52nd highest of 1553.5%12.7%Bending strength
12,300 psi84.8 MPa64th weakest of 1554,300 psi29,900 psiStiffness
1.59 M psi11.0 GPa66th most flexible of 1550.54 M psi4.06 M psiDensity
0.480.55 at 12% MC71st lightest of 1550.250.96Janka hardness
910 lbf4,048 N76th softest of 15534th of 53 U.S. hardwoods240 lbf3,680 lbf
How much it moves
The two directions move almost alike (T/R 1.37), so flatsawn and quartersawn boards differ by only 0.14 in.
0.52 in.
off a 6-inch flatsawn board, green to oven-dry
- Tangential
- 8.6%
- Radial
- 6.3%
- Volume
- 16.2%
- T/R ratio
- 1.37 (10th most stable of 155)
End view, shrinkage drawn 3× life size.
Closest substitutes
- Black walnut
11% harder · 6% heavier · shrinks 0.8 points less across the face
- Cucumbertree
23% softer · 8% lighter · shrinks 0.2 points more across the face
- Black ash
7% softer · 6% lighter · shrinks 0.8 points less across the face
Among the birches
3rd hardest of 3, lbf.
Laboratory values
| Property | Green | Dry, 12% MC | Change when dried | Metric, 12% MC |
|---|---|---|---|---|
| Work to maximum load | 16.2in-lbf/in³ | 16in-lbf/in³ | −1% | 110.3kJ/m³ |
| Compression parallel to grain | 2,360psi | 5,690psi | +141% | 39.2MPa |
| Shear parallel to grain | 840psi | 1,210psi | +44% | 8.30MPa |
| Compression perpendicular | 270psi | 600psi | +122% | 4.10MPa |
| Impact bending | 49in. | 34in. | −31% | 864mm |
| Modulus of rupture | 6,400psi | 12,300psi | +92% | 84.8MPa |
| Modulus of elasticity | 1.17M psi | 1.59M psi | +36% | 11.0GPa |
| Side hardness | 560lbf | 910lbf | +62% | 4,048N |
| Tension perpendicular | 380psi | not tested | — | — |
Wood Handbook Table 5-3b, Table 4-3. Data & method · Guides