Symptoms
- Visible gaps between floorboards
- Gaps more noticeable in winter, less in summer
- Dust or debris collecting in the gaps
- Gaps consistent across most of the room
Likely causes
- CommonNormal seasonal humidity changesWood shrinks in dry winter air and expands again in humid summer, causing gaps to open and close.
- CommonLow indoor humidity, especially with forced-air heat runningHeating systems dry out indoor air significantly in winter, shrinking wood more than usual.
- PossibleWood installed too dry or too wet originallyIf boards weren't acclimated properly before installation, gapping can be more pronounced.
- PossibleGradual wood shrinkage with ageVery old floors can develop permanent gaps as the wood fully dries out over decades.
What to do
- Check whether gaps close up again in summer; if so, this is likely normal seasonal movement, not a defect.
- Use a home humidifier in winter to keep indoor relative humidity in a healthier range, which reduces gapping.
- Avoid using a whole-house humidifier setting so high that it causes condensation on windows.
- For gaps that stay open year-round, clean out debris with a vacuum crevice tool so dirt doesn't compact and wear the board edges.
- For minor permanent gaps, a color-matched wood filler or specialized gap-filling rope product can be pressed into the seams.
- For widespread, wide, permanent gapping, a flooring pro can weave in thin wood filler strips or, in severe cases, recommend replacement boards.
- Monitor humidity with an inexpensive hygrometer to catch swings before they cause excessive movement.
Tools and parts
- Vacuum with crevice tool
- Hygrometer
Wood floor gap fillerSearch: “hardwood floor gap filler rope”
When to call a pro
Call a flooring contractor if gaps are wide, permanent, and affect a large area, since that may need professional filling or board replacement.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.