Stop Squeaky Floors

Shimming the subfloor: If floor joists are not tight against the subfloor in the area that's squeaking, shimming may solve the problem. Wedge shims between the joist and subfloor and tap them into place. Don't pound the shims because they could lift the floorboards and cause more squeaking.
Cleating the subfloor: Where several boards in the subfloor above a joist are moving, securing them with a cleat works better than shimming the boards individually. A piece of 1x4, wedged against the subfloor and nailed to the joist solves this problem.
Reinforcing joists: Squeaking over a large area may indicate that the joists beneath the floor are shifting slightly and inadequately supporting the subfloor. Steel bridging, nailed between joists, keeps the joists from moving side to side and stabilizes the subfloor.
Driving screws from below: Drill a pilot hole through the subfloor, then a smaller pilot hole into the finished floor. Have someone stand on the raised boards while you pull them tight with a wood screw.
Nailing from above: When you can't get access to the floor from below, drill pilot holes and nail through the surface. Locate the floor joists and nail directly into them for a fastening job that won't work loose. Countersink the nail heads.
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