Mysterious stains found under old flooring: Is it mold and should I worry?
Stains uncovered during flooring removal often look suspicious and worrisome, leaving homeowners unsure whether to treat the subfloor or simply ignore it. This uncertainty prevents people from finishing their flooring replacement projects safely without second-guessing potential damage.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
Mysterious stains found under old flooring: Is it mold and should I worry?
- 1Vacuuming up the debris and laying new flooring directly over itDid this help you?
- 2Applying a stain-blocking primer like Kilz over the area before proceedingDid this help you?
- 3Ignoring the stain if it shows no odor or major structural warpingDid this help you?
- 4covering the hole with another box while unsure how to proceedDid this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“Any idea what it could be? I put the tile I took up in a box ready for the skip Tommorow and covered the hole with another box but unsure what it could be and a bit worried about lifting up the rest of the tiles under!”source ↗
Where this came up
People with this problem also raised
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- 2Finding construction debris and mystery layers under old flooring
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