Definition
The subfloor is the layer of plywood between your joists and finished flooring. Water damage turns it to mush—when your floor feels soft or squishy, the subfloor is likely rotted underneath.
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Subfloor material and condition affect floor system performance and cost to repair. Water damage, rot, or improper fastening compromises structural integrity and creates soft spots or squeaks. Inspectors assess subfloor condition by examining crawl spaces and basements, looking for signs of moisture damage, deterioration, or inadequate support. Replacement is expensive and disruptive.
Pro Tip
Soft or bouncy floors signal subfloor problems. Get a professional evaluation—subfloor replacement is expensive and disruptive.
Example
A buyer's inspector found subfloor damage in a bathroom where a shower pan had leaked for years. The subfloor had rotted completely and required removal of the finished flooring, replacement of damaged subfloor and joists, and installation of new shower pan and floor finish—a $12,000 repair.