· Michael Blair
A squeak is friction between two components that should be fixed together. Identifying which pair is moving is the whole job, because the fix from below is straightforward and the fix from above is not.
The three common sources
Subfloor lifting off the joist, so the nail shank rubs in its hole as you step. This is the classic squeak and the most common in Nashville houses with nailed rather than glued subfloor.
Hardwood boards rubbing against each other, most often in dry winter conditions when they have shrunk. And bridging or blocking between joists that has loosened and moves.
Fixing from below
If there is a crawl space or an unfinished basement, this is the good outcome. Shims driven into the gap between joist and subfloor with adhesive, or a bracket that pulls the two back together.
Have someone walk above while you locate it. The movement is usually visible from underneath, which makes the repair precise rather than speculative.
- Locate the movement with someone walking above
- Shim with construction adhesive, do not force the shim
- Use brackets where the gap is wider
- Add blocking where joists are moving laterally
- Screw rather than nail — nails caused it originally
Fixing from above
Harder, because the fix has to go through the finish floor. Specialist screws that snap below the surface work through carpet and can work through hardwood with the head filled.
On hardwood, powdered graphite or talc worked into the seam lubricates board-on-board squeaks and is worth trying first, since it is reversible and costs almost nothing.
When it means something more
A squeak that appears suddenly across a large area, or that comes with visible deflection or a sloping floor, is worth investigating properly. That can indicate a failed joist, a compromised support post, or crawl space moisture damage.
In Middle Tennessee, crawl space moisture is the usual culprit behind structural softening, and the squeak is the symptom that gets noticed first.