Flooring · Common problems · Updated November 2026
Flooring Gaps, Buckling and Cupping: How They Differ
Wood and wood-based floors move with humidity. The shape of the problem is a strong clue to the cause, and the cause has to be fixed before the floor can be repaired.
The patterns
| Pattern | What it looks like | Common causes |
|---|---|---|
| Gaps | Spaces between boards, often in winter | Dry indoor air; normal seasonal movement in many wood floors |
| Cupping | Board edges higher than the centers | Moisture from below: crawl space, basement, slab or a leak |
| Crowning | Board centers higher than the edges | Often a cupped floor sanded flat too early, or moisture from above |
| Buckling | Boards lifting off the subfloor | Flooding or a major leak; or a floating floor without enough expansion space |
| Peaking (floating floors) | Joints lifting into a ridge | Floor pinned by cabinets or trim, or missing expansion gaps |
What you can safely check
- Measure indoor humidity (how to measure).
- Look for leaks from dishwashers, refrigerators, sinks and exterior doors.
- Check the crawl space or basement below for moisture (crawl space moisture).
- For floating floors, check whether trim, cabinets or transition strips are pinning the floor at the edges.
Next steps
- Gaps: often close as humidity rises; a humidifier can help in winter.
- Cupping: fix the moisture source and let the floor dry; it may flatten on its own. Do not sand until it has dried.
- Buckling: usually needs the source fixed and affected boards replaced; check the subfloor (subfloor repair).
Check the flooring warranty, which often requires specific humidity ranges and expansion gaps. Replacement options: flooring cost for 1,000 sq. ft. and installing over existing floors.
Cost figures are national ranges from the sources listed in our flooring cost guide, not a quote from FixFinch or any contractor. This article is general information to help you decide on next steps. It is not an inspection or professional advice; a qualified pro who sees the problem in person can tell you what is actually going on.