Red alder (Alnus rubra) in numbers: hardness, weight, strength, shrinkage, movement and decay resistance, taken from the tables of the USDA Forest Products Laboratory’s Wood Handbook, followed by what the wood is like to work and what it is used for. The values are averages from small, clear, straight-grained test specimens; real boards with knots, sloping grain or a different moisture content will differ.
| Property | Red alder |
|---|---|
| Janka side hardness, 12% moisture | 590 lbf (2,624 N) |
| Janka side hardness, green | 440 lbf |
| Hardness rank | harder than 46 of the 168 woods with a 12% hardness value in our database |
| Density at 12% moisture | 28.7 lb/ft³ (459 kg/m³) |
| Weight per board foot (12%) | 2.39 lb |
| Specific gravity (ovendry weight, green volume) | 0.37 |
| Specific gravity at 12% moisture | 0.41 |
| Bending strength (modulus of rupture), 12% | 9,800 psi |
| Stiffness (modulus of elasticity), 12% | 1.38 million psi |
| Crushing strength (compression parallel to grain), 12% | 5,820 psi |
| Shrinkage green to ovendry: radial / tangential / volumetric | 4.4% / 7.3% / 12.6% |
| Tangential / radial shrinkage ratio | 1.66 |
| Dimensional change per 1% moisture (radial / tangential) | 0.00151 / 0.00256 |
| Impact bending (drop height to failure), 12% | 20 in. |
| Heartwood decay resistance | slightly or nonresistant |
What it is
Red alder (Alnus rubra) grows along the Pacific coast between Alaska and California. It is the principal hardwood for the commercial manufacture of wood products in Oregon and Washington, and the most abundant commercial hardwood species in those two states.
The wood varies from almost white to pale pinkish brown, and there is no visible boundary between heartwood and sapwood.
Working properties
Red alder is moderately light in weight and intermediate in most strength properties, but low in shock resistance. It has relatively low shrinkage: 7.3% tangentially from green to ovendry, and in service a flatsawn board changes width by about 0.256% for each 1% change in moisture content.
Weight and density
At 12% moisture content red alder weighs about 28.7 lb per cubic foot, so one board foot (144 cubic inches) weighs about 2.39 lb. An 8 ft board of actual size 3/4 × 5-1/2 in. (a 1×6) holds 0.229 cubic feet and weighs about 6.6 lb; an 8 ft piece 1-1/2 × 3-1/2 in. (a 2×4 size) weighs about 8.4 lb. Green wood is much heavier because of the water it holds.
Density here is ovendry weight plus 12% water, divided by volume at 12% moisture content (Wood Handbook Eq. 4-12: density = specific gravity at 12% × 62.43 lb/ft³ × 1.12).
Wood movement
The Wood Handbook gives dimensional change coefficients for each species: the fraction of its width a board gains or loses for every 1% change in moisture content, between about 6% and 14%. For red alder they are 0.00256 across a flatsawn face (tangential) and 0.00151 across a quartersawn face (radial).
Worked example: a flatsawn board 7-1/4 in. wide (a nominal 1×8) that goes from 6% moisture content in a heated winter house to 12% in a humid summer changes width by 7.25 × 0.00256 × 6 = 0.111 in. (about 1/8 in.). The same board quartersawn moves 0.066 in. (about 1/16 in.). Allow for this in panels, tabletops and floors; the wood movement calculator works it out for any size and moisture range.
How it compares
| Species | Janka (lbf) | Density (lb/ft³) | Bending (psi) | Stiffness (Mpsi) | Tangential shrink (%) | Decay resistance |
|---|---|---|---|---|---|---|
| Red alder | 590 | 28.7 | 9,800 | 1.38 | 7.3 | slightly or nonresistant |
| Black cherry | 950 | 35.0 | 12,300 | 1.49 | 7.1 | moderately resistant |
| Yellow-poplar | 540 | 29.4 | 10,100 | 1.58 | 8.2 | slightly or nonresistant |
| Red maple | 950 | 37.8 | 13,400 | 1.64 | 8.2 | slightly or nonresistant |
| American basswood | 410 | 25.9 | 8,700 | 1.46 | 9.3 | slightly or nonresistant |
| Black walnut | 1,010 | 38.5 | 14,600 | 1.68 | 7.8 | resistant |
Uses
The principal use of red alder is furniture. It is also used for sash and door panel stock and other millwork.
Frequently asked questions
How hard is red alder?
Red alder averages 590 lbf (2,624 N) on the Janka test at 12% moisture content and 440 lbf green, softer than black cherry (950 lbf) and red maple (950 lbf).
Is alder a hardwood?
Yes. Red alder is a hardwood and the most abundant commercial hardwood in Oregon and Washington, but it is moderately light in weight and, at 590 lbf, softer than cherry, maple or walnut.
Is red alder stable?
The Handbook describes red alder as having relatively low shrinkage. In service a flatsawn board changes width by about 0.256% and a quartersawn board by about 0.151% for each 1% change in moisture content.
Can red alder be used outdoors?
Not untreated. Its heartwood is in the slightly or nonresistant decay class, so it needs preservative treatment or a protected location outdoors.
Sources
- USDA Forest Products Laboratory. Wood Handbook: Wood as an Engineering Material. General Technical Report FPL-GTR-190, 2010. Chapter 2 (species descriptions), Chapter 4 (Tables 4-3, 4-4 shrinkage; Eq. 4-7, 4-9, 4-12 density), Chapter 5 (Tables 5-3b, 5-5b strength and hardness), Chapter 13 (Table 13-5 dimensional change coefficients), Chapter 14 (Table 14-1 decay resistance)
- USDA Forest Products Laboratory. Wood Handbook, 2021 edition (FPL-GTR-282)
Last reviewed: 24 October 2026. Numbers are generated from our parsed copy of the Handbook tables, so every page uses the same data. Values marked * are estimates computed with the Handbook’s own equations. Spotted an error? Please let us know.