You’ve spent time planning your cottage project—now take the time in the building centre to buy lumber that’s not warped. Here’s what to look for with each board off the pile.
Bring one end up to eye level; close one eye and look along a face and then an edge. Inspect for any of these deviations from a straight line.
A corkscrew rotation is okay if it’s mild enough that you can clamp the board flat before fastening. Like any warp, it’s easier to straighten thin, flexible 1″ boards than thicker 2″ lumber.
A curve along an edge is near impossible to remedy, so unless you’re cutting short pieces, put the board aside—please!
When the ends curl in, like skis. That’s not good for deck boards, although you may be able to clamp a mild bow and hold it down with deck screws.
Opposite edges curling in. A little is actually an asset if the board is going to be installed flat: place it crown up, and water will run off it. But too much can lead to splitting.
Avoid boards with large knots!