Should I fill unknown holes in my basement wall?
Unexplained basement holes, especially those near plumbing pipes or opening directly to dirt, might be intentional weep holes for drainage. Because it is unclear if these gaps serve a specific purpose, people are forced to halt their painting and wall prep. They cannot safely apply hydraulic cement or seal the wall without knowing if the hole needs to stay open.
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.
Should I fill unknown holes in my basement wall?
- 1filling them with hydraulic cementDid this help you?
- 2drilling into the holes to clean them out before sealingDid this help you?
- 3Using hydraulic cement to plug the opening.Did this help you?
- 4Filling the void with high expansion foam insulation.Did this help you?
- 5Stuffing the hole with rock wool insulation and capping it with an aluminum sheet and caulk.Did this help you?
- 6Mixing up concrete to fill and smooth over the hole.Did 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'm in the process of filling minor holes (tie-straps etc.) with fastplug hydraulic cement prior to painting. I've found several holes near the place where septic tank outlet pipe exits the wall underground, that look like they are intentional, and I'm wondering if they are weep holes or similar that I need to keep open.”source ↗
“Would love a suggestion on how to seal this hole in the basement. I’m not sure what was here prior but it just opens to dirt. How should I seal this, and should I or would there be a reason to have access to this?”source ↗
Where this came up
People with this problem also raised
- 2How to fill a deep concrete void under a slab or wall
- 5How to frame and insulate basement walls
- 31Should I use foam or caulk to seal gaps in exterior walls?
- 3Can I insulate and finish basement walls if they get damp?
- 2How to retrieve something dropped down a wall cavity
- 2Horizontal crack behind basement paneling: how worried should I be?