Choosing a wood species: hardness, weight and stability compared

What the numbers mean

• Janka hardness — the force needed to press a steel ball halfway into the wood, in pounds-force (lbf). Higher means more dent resistance. It is a useful ranking, not a guarantee.
• Density — dried weight at about 12% moisture. Heavier woods are generally harder and stronger, and heavier to move around.
• Tangential shrinkage coefficient — how much a flatsawn board changes width per 1% change in moisture content. Lower is more stable.

Matching wood to the job

Tabletops, desks and floors

Surfaces that take abuse benefit from harder woods: hard maple, white oak, red oak, ash and hickory. Walnut and cherry are softer and will show dents over time, which many people accept as character. Softwoods like pine dent easily but are inexpensive and look good aged.

Outdoor projects

For decks, fences and outdoor furniture, what matters is rot resistance. Pressure-treated southern yellow pine is the most common choice for structure and decking. Western red cedar and redwood heartwood have natural decay resistance and are light and stable. White oak heartwood is far more decay-resistant than red oak, whose open pores wick water — which is why white oak, not red, is used for barrels and boats.

Painted furniture and built-ins

Poplar is the default: inexpensive, fairly stable, easy to machine, and its green streaks disappear under paint. Soft maple and MDF are alternatives. Pine takes paint but knots can bleed through without a stain-blocking primer.

Shelving

Stiffness matters more than hardness for shelves. Denser hardwoods such as oak, maple, ash and birch sag less than pine at the same thickness. Use the shelf sag calculator to compare — the worked example Will a 1x12 pine shelf sag over 36 inches shows where softwood starts to struggle under a load of books.

Wide panels and doors

Stability is the priority. Cherry, walnut and mahogany move less than oak, maple or beech. Quartersawn lumber of any species moves roughly half as much across its width as flatsawn, and riftsawn falls in between. Two worked examples put numbers on it: How much a 36 inch red oak tabletop moves and How much a 900 mm walnut tabletop moves.

Workability

• Easy: pine, poplar, basswood, cedar, cherry, walnut and mahogany cut, plane and sand without much fuss.
• Moderate: oak and ash are hard but straightforward; the open grain may need filling for a glass-smooth finish.
• Demanding: hard maple and hickory are hard on tools and prone to burning on saws and routers. Figured grain in any species tears out easily.
• Blotchy to stain: pine, cherry, maple and birch absorb stain unevenly. Use a pre-stain conditioner or a gel stain, or skip stain altogether.

Cost and availability

Local and common species cost less: in much of North America that means pine, poplar, red oak and soft maple. Walnut, cherry and white oak cost more, and imported tropical woods more still. Prices vary widely by region and over time, so compare per board foot at your local dealers rather than relying on national averages.

Softwood vs hardwood

The names describe the tree, not the wood. Softwoods come from conifers (pine, fir, spruce, cedar); hardwoods from broadleaf trees (oak, maple, cherry, poplar). Most softwoods are softer than most hardwoods, but not all: Douglas-fir is harder than basswood, and southern yellow pine is harder than poplar. For a project, look at the actual hardness, stiffness and stability numbers rather than the category.

Softwoods dominate construction because they grow fast and straight and are sold in standard dimensional sizes. Hardwoods dominate furniture because of their hardness, figure and the way they take a finish.

Sustainability

Many domestic hardwoods are widely available from managed forests. For imported species, look for certification from a recognized scheme such as the Forest Stewardship Council (FSC), and avoid species listed as threatened. Local sawyers with urban or storm-fallen logs are another good source.

Weight

Density decides how heavy a project will be to move. A solid white oak dining table can weigh roughly twice as much as the same table in white pine. Estimate before you commit, especially for pieces that must be carried upstairs or hung on a wall. The densities above are for dry wood; freshly sawn slabs from a local sawyer carry a lot of water, and a green red oak board weighs about 40% more than the same board dried.

• Hardwood by the board foot: How much does a board foot of oak weigh — about 3.6 lb for red oak, a quick way to weigh a whole lumber order.
• Framing lumber: How much does a 2x4x8 weigh compares spruce-pine-fir with the denser southern yellow pine, and Weight of 45 × 95 mm × 2.4 m timber does the same for Scots pine and spruce whitewood.
• Sheet goods: if a carcase is plywood or MDF rather than solid wood, How much does a sheet of 3/4 plywood weigh compares plywood, OSB and MDF; for a floor, count the sheets first with How many sheets of plywood for a 12x12 subfloor.
• Firewood: density also sets how much a cord weighs and how much heat it holds — How much does a cord of oak weigh compares species on the same basis.