Why is my subfloor wavy and dropping?
Subfloors can drop and feel wavy or roll when long-term damage causes structural sections to cave in. This leaves homeowners dealing with progressive floor failure on their own because insurance typically excludes long-term damage, preventing them from safely finishing renovations until the underlying structure is repaired.
What the numbers show
Counted from the threads quoted below. How we count
- The most recent one is from October 2026.
- This comes up 42.2× 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.
- 1Hiring expensive restoration companies like ServProDid this help you?
- 2Waiting for contractor estimates while trying to prevent further damageDid this help you?
- 3Relies on friends who dabble in HVAC and handy friends for helpDid this help you?
- 4Filling the damaged area with self-leveling concrete before installing carpetDid this help you?
- 5Sourcing replacement parquet squares to patch the missing area before laying carpetDid this help you?
- 6filling gaps with caulk to air seal themDid this help you?
- 7using floor leveling compound to take out dipsDid this help you?
- 8laying down vinyl sheet to make it waterproof and cheaperDid this help you?
- 9pulling staples, nails, and tack strips and painting with kiln primer to lock in odorDid this help you?
- 10Getting a second opinion from a different professionalDid this help you?
- 11Ensuring the contractor properly grinds high spots on the slab before installationDid 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.
“I have no experience and just needed to rip of this carpet in my laundry room (cat piss) and fount these huge gaps and un level sub floor”source ↗
“And on a tight tight budget…like st vinnys/free store budget…”source ↗
“Also Got this flooring for free from mom but no way to cut it.”source ↗
“My hubby and I disagree on how to resolve this.”source ↗
“Honestly I don’t care how we fix it, but I want to go the budget, but not something that doesn’t work, route. Any suggestions are appreciated.”source ↗
“a portion of our floor caved in.”source ↗
“i have no clue what to do here.”source ↗
“it’s getting progressively worse by the day, last night we had more subfloor fall but the laminate did not come down so that’s holding another hole at this point.”source ↗
“my home owner’s insurance stated this was long term damage and therefore not covered by anything with them, so we’re on our own here.”source ↗
“The new flooring is unlevel in points, feels a bit soft in spots.”source ↗
“i had similar thing with my kitchen floor last year, contractor said it was ready but when the vinyl went down you could feel little waves in 2 corners.”source ↗
“Also some doors if not shut all the way open up wondering if that may be a sign of the not perfectly flat”source ↗
Where this came up
People with this problem also raised
- 39How to tile over an uneven subfloor without tearing it up
- 2Sudden split and missing chunks in bathroom subfloor
- 7Why is my apartment flooring bubbling and getting gaps after cleaning?
- 4Should I add plywood to a flexing subfloor or replace it?
- 5What to do about a bad hardwood floor installation
- 2Who to call when a wood floor starts buckling after a flood?