An investor finds stained subfloor in two bedrooms mid-renovation

The situation

Illustrative example. Not a real job or customer.

An investor buys a 1970s split-level in a suburban part of the metro to renovate and resell. The house had a strong stale odor in two upstairs bedrooms that the investor assumed came from the carpet. When the carpet and pad come up, the plywood subfloor in both rooms has large dark stains, the tack strip is black along one wall, and the smell is stronger than before.

1. The investor pauses flooring installation and asks for an assessment before any decision.
2. Stained areas are marked. From the floor below, one stain is visible through the ceiling drywall, meaning liquid went through the subfloor.
3. The section of subfloor with the through-stain is cut out and replaced by a carpenter, and the joist below is cleaned and treated.
4. Remaining stained areas, which are sound but discolored, are cleaned, treated and allowed to dry over several days.
5. Two coats of an odor-blocking sealer are applied to all treated areas, with a closed-room check after each.
6. All tack strip in both rooms is replaced, and the lower drywall and baseboard along the worst wall are removed and replaced.
7. The stained ceiling drywall below is cut out, replaced and primed.
8. Only after a final closed-room recheck do the installers lay new pad and carpet.

The schedule slips by about a week, but the bedrooms smell neutral at final walkthrough and the investor has photos of every step for the listing agent. The alternative, sealing over the through-stain, would likely have left an odor that buyers or their inspector noticed.