Subfloor Preparation Inspection

Subfloor must be flat (3/16" in 10 feet for most flooring), dry, clean, and securely fastened to joists. Squeaks indicate loose areas.

1. Check flatness with a 10-foot straightedge — maximum 3/16" deviation for most finish flooring

2. Walk the entire subfloor — feel for soft spots, squeaks, or bouncing

3. Check moisture content with a moisture meter — should be below manufacturer specs for finish flooring

4. Verify subfloor is properly fastened — screws preferred over nails (less squeaking)

5. Check for gaps between plywood panels (should be 1/8" expansion gap)

6. Verify panel edges are supported on joists (no unsupported edges)

7. Check for any damaged, delaminated, or water-stained panels

8. Verify subfloor type is compatible with intended finish flooring

- Subfloor not flat (finish flooring telegraphs imperfections)

- Squeaky subfloor (needs re-fastening before finish flooring)

- High moisture content (damages finish flooring)

- Unsupported panel edges (flex creates bumps in finish floor)

- Damaged or delaminated panels (soft spots)

- Wrong subfloor type for finish flooring (e.g., particle board under hardwood)