Squeaking or creaking hardwood floor

Noise underfoot in specific spots, usually worse in the dry months. Wood-on-nail is a sharp chirp; wood-on-wood is a lower groan; a hollow knock is the subfloor moving against the joist.

What causes it

In rough order of likelihood. Each one has a tell — the observation that separates it from the others.

1. 1

   The subfloor moving against a joist

   How to tell: A deeper knock rather than a chirp, along a line rather than at a point, and it moves underfoot when someone else walks past.

2. 2

   Fasteners that have lost their grip

   How to tell: A sharp chirp at a specific spot, worst in winter when everything has shrunk.

3. 3

   Boards rubbing at their tongue and groove

   How to tell: A dry rasp that appears in the heating season and eases in summer. Often just low humidity.

4. 4

   Inadequate subfloor prep at installation

   How to tell: A newer floor that squeaked from the first winter, over a wider area than a single joist would explain.

What it actually means

Almost every squeak is movement between two pieces of wood, or between wood and a fastener. On a century house it is largely cosmetic. On a five-year-old floor it usually points at what was under the boards when they went down.

Most squeaks can be quietened. From below, through the subfloor, is the right way where there is access — nothing shows in the finished floor. From above means face-screwing and plugging, which is visible, so we only do it where there is no other route.

• Raise winter humidity to 35–50% first. A surprising number of squeaks go quiet on their own.
• Mark the exact spots with tape while they are noisy. They are much harder to find on the day.
• If there is access from below, look for a visible gap between subfloor and joist while someone walks above.
• Do not pour talc or powder into the seams. It is a two-week fix that contaminates the boards for any future refinish.

• Gaps opening between boards in winter
• Hollow-sounding or bouncy spots underfoot