How to spot hidden subfloor damage covered by new OSB
Sellers sometimes cover up subfloor staining, mold, or urine by laying new OSB right over it. Buyers are left guessing whether the underlying issue was actually fixed or if they are inheriting a costly hidden problem before closing.
What the numbers show
Counted from the threads quoted below. How we count
- This comes up 37.6× more often in r/Flooring than across the site as a whole.
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.
How to spot hidden subfloor damage covered by new OSB
- 1guessing it needs the subfloor ripped out and replacedDid this help you?
- 2putting down new OSB and covering with LVPDid this help you?
- 3watering the foundation during dry periods to keep clay soil from shrinkingDid this help you?
- 4calling a structural engineer to assess the damage and remediation optionsDid this help you?
- 5Replacing subfloors with plywoodDid this help you?
- 6Installing luxury vinyl plank (LVP) and rugsDid this help you?
- 7Dealing with multiple layers of vinyl flooringDid this help you?
- 8Hiring an independent contractor specializing in mold to inspect and do repairsDid this help you?
- 9Asking for a specialist to evaluate before closingDid this help you?
- 10Walking away from the purchase or bouncing immediatelyDid 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.
“Foundation showing cracks after 6 years. This is our first home so we don’t know jack. Is there a repair for this or do we leave it as is?”source ↗
“The other one is on driveway but near the foundation. Not sure to do about that one either.”source ↗
“I hired an independent inspection and when the inspector returned to grab the radon testing kit he noticed mold on the bottom of the floor joists.”source ↗
“the power went out the basement got wet etc. I was told it was dried out and that it wouldn’t be an issue but today I realized that may not be the case.”source ↗
“it worries me that it could be behind the walls all over the house….”source ↗
“Just bought my first home and picked up the keys this week. Went to work removing the carpet in the bedrooms and did not win the “hidden hardwood floors” under the carpet lottery.”source ↗
“Feel your pain dude. I replaced half my house last year with plywood now I have to do the other half this year.”source ↗
“curious if we are looking at mold, pet staining, or _____. We do know they placed new OSB over it. This is out of my wheelhouse and if anyone has any idea we would appreciate it.”source ↗
“My biggest curiosity is if I should be concerned if they didnt actually remove the issue if it's urine or mold.”source ↗
“Not excited for that”source ↗
Where this came up
People with this problem also raised
- 15How to tell if a discounted house has major foundation damage
- 2Horizontal crack behind basement paneling: how worried should I be?
- 17Unexplained holes or damage inside the house
- 3Found no subfloor under sagging floor
- 5What to do if your rental house has severe structural damage
- 2Should I buy a house with extensive basement mold?