Flooring problems

Cupping - board edges higher than the centers - means the underside of the floor is wetter than the top. The cause is under the floor: a damp crawlspace, a slab without a vapor barrier, or a leak. Sanding a cupped floor flat before the moisture is fixed and the wood has dried is the classic wasted repair. It will cup again, and now the boards are thinner.

Gaps between boards in winter and tightness in summer is normal seasonal movement in solid wood. Gaps you can drop a coin into, gaps that persist year-round, or boards that have pulled away from a wall are not normal - that is an acclimation or fastening problem.

Laminate and click-lock vinyl that peaks up in the middle of the room almost always means no expansion gap was left at the perimeter, or the flooring was pinned by a heavy cabinet, transition strip or nailed-down baseboard. The floor has nowhere to grow, so it grows upward. This is an installation defect, and it is worth pressing the installer on.

Squeaks are movement between the finish floor, the subfloor and the joists. From above, they are sometimes fixable with screws and shims; from an unfinished basement below, they are much easier. If the squeaking comes with visible bounce or sloping, stop treating it as a flooring issue - floor joist work runs about $125-$315 per joist and belongs to a structural contractor.

Discovering mold under an old floor is common and expensive: remediation runs about $10-$25 per square foot. Do not let a flooring crew simply cover it up.