Buying Lumber in Ontario

SIZES The name is not the size

Dimensional lumber is named for its rough size before drying and planing. What you bring home is smaller — and that smaller size is the one your plans must use.

1. Measure before you design around itA tape measure in the store settles arguments your project can’t afford. Plywood sold as “3/4 in” is often 23/32 in (18 mm) — close, but your dados will notice the difference.

BOARD FEET Board feet: hardwood is sold by volume

Lumberyards price hardwood by the board foot — a volume measure — because yard boards come in random widths and lengths.

1. The formulaBoard feet = thickness (in) × width (in) × length (ft) ÷ 12. That single equation covers every board in the yard, whatever its shape.
2. A worked exampleAn oak board 1 in thick, 6 in wide, 8 ft long: 1 × 6 × 8 ÷ 12 = 4 board feet. At $7 a board foot, that’s a $28 board — whatever the handwritten tag’s total seems to say.
3. Rough, S2S, S4SRough lumber is cheapest but needs a jointer and planer you may not own. S2S (surfaced two sides) has flat faces; S4S (surfaced four sides) is ready to cut. As a beginner, paying for S4S is paying rent on machines you skipped — worth it.
4. Quarters are thickness4/4 is read “four-quarter” and means roughly 1 in thick in the rough; 8/4 is 2 in. It’s the yard’s shorthand, not a fraction to do math with.

PICKING Picking boards that behave

1. Sight down every boardHold one end at eye level and look along it: bow (curve along the length), crook (curve along the edge), twist (a spiral), and cup (curve across the width) all show up in silhouette. A mild bow can be worked around; twist can’t.
2. Check the ends and the stampEnd splits only grow. On construction lumber the stamp tells the story: in Ontario it’s usually SPF — spruce, pine, or fir — graded No. 2 for general use, and KD-HT means kiln-dried and heat-treated: dry enough to build with indoors.
3. Big-box vs lumberyard, honestlyBig-box pine boards are convenient, consistent, and priced per board — fine for painted projects and practice. Lumberyards win on hardwood selection, price per board foot, rough stock, and staff who will surface and crosscut for a small fee.
4. Buy 10–15% extra, then acclimateThe extra covers the knot you didn’t see and the cut you’ll miscut. At home, stack boards flat with thin sticks (stickers) between the layers for several days, so they adjust to your shop’s air before you cut them to size. And mind your fingers: rough lumber and big-box splinters are the most common cut in the whole hobby — gloves for carrying, off for machining.

WATCH OUT Common beginner mistakes

1. Taking the top boardThe top of the pile is the board everyone else rejected. Dig for the straight ones — and restack the pile neatly when you’re done.
2. Pressure-treated for indoorsPT lumber is wet, heavy, and treated for outdoor rot resistance — wrong for furniture and miserable to finish. Indoor projects get kiln-dried stock.
3. Buying exactly the cut listZero-waste math meets one hidden knot, and the project stops for a week. The 10–15% buffer is the cheapest schedule insurance in the shop.
4. Milling the day you buyWood moves as it equalizes with your shop’s air. Cutting to final size on day one is how flat boards become curved parts by the weekend.

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