Nine woods, two numbers: choosing timber for a Venice accent wall

Walk into a lumberyard with a picture of a finished wall and you will be asked one question first: which wood? It is tempting to answer by color alone. Yet two measurable traits decide how a board ages on a living-room wall in Venice: how easily it dents, and how much it swells and shrinks as the air changes. The federal Wood Handbook publishes both for dozens of North American species¹.

What does “side hardness” measure?

The Handbook defines side hardness by a modified Janka test: the load needed to push a 0.444-inch ball into the wood to half its diameter, averaged across the board’s radial and tangential faces and reported in pounds-force (lbf)¹. Higher numbers mean a wall that shrugs off a stray chair back or vacuum bump. For a wall that people brush past every day, such as a hallway or the space behind a dining table, the number matters more than on a wall that sits behind a bed.

How much does each species move?

Wood swells as it picks up moisture and shrinks as it gives moisture up. The Handbook gives a dimensional change coefficient for each species that applies between roughly 6% and 14% moisture content. Multiply it by the board width and by the change in moisture, and you have an estimate of how much the board will grow or shrink¹.

The last column below applies that formula to a common case: a flatsawn board 5.5 inches wide (the face width of a typical “1x6”) moving from 8% to 11% moisture. Those two figures are not arbitrary. The Handbook recommends about 8% for interior woodwork in most of the country and about 11% in damp, warm coastal areas, which on its map include Florida¹.

Specific gravity and side hardness: Wood Handbook Table 5–3b (small clear specimens, 12% moisture content). Coefficients: Table 13–5. Width change calculated by Grain & Light with Handbook Eq. 13–2: change = width × C_T × (final MC − starting MC).

Which woods suit which walls?

Oak, maple and walnut sit at the hard end of the table, which makes them the safe picks for high-traffic walls. They also move the most among the woods listed here, with oak and maple near six hundredths of an inch per board in our example. That is invisible on one board but adds up across a wall.

Cherry is the quiet compromise: moderately hard, with the smallest tangential coefficient of the hardwoods here.

Baldcypress and western redcedar are soft, so a fingernail can mark them, but they move the least. They make sense for walls that are looked at more than touched, and for designs with tight, closed joints where a gap would show.

Yellow-poplar is soft, at 540 lbf. If the wall will be painted, hardness still counts in a busy spot, but a painted finish hides grain and color differences, so smooth machining and good primer adhesion become the bigger questions.

Longleaf pine lands in the middle on both counts, at 870 lbf and a coefficient of 0.00263, with a warm, resinous look of its own.

Does the way a board is sawn matter?

Yes. A flatsawn board, with growth rings roughly parallel to its face, changes width according to the larger tangential coefficient. A quartersawn board, with rings on edge, follows the smaller radial coefficient. For white oak the Handbook lists 0.00365 tangential against 0.00180 radial, so a quartersawn oak board moves about half as much across its width¹. The Handbook also notes that most commercial lumber is neither perfectly flatsawn nor quartersawn, so the formula tends to overestimate width change for mixed stock.

What should you ask before choosing?

Ask what moisture content the boards were dried to, whether they are flatsawn or quartersawn, and how long they can sit in the room before installation. Our humidity explainer covers why that last question is the one people skip.