How to fill a deep concrete void under a slab or wall
Deep, hard-to-reach wall and slab voids make it difficult to pour or pack material all the way to the top without leaving empty gaps. Without a proper method to squeeze the mix in, the cavity cannot be filled to the brim, leaving the structure vulnerable to sinking.
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 fill a deep concrete void under a slab or wall
- 1Using high density expansion foam as a DIY fixDid this help you?
- 2Building a hopper and pouring liquid grout into the voidDid this help you?
- 3Hiring a mud jacking professionalDid this help you?
- 4Selling the houseDid 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.
“Found a hole under my driveway and stuck a stick in to see how deep it was. I could stick it all the way in (about 80cm) and wave it around underneath the slab. What can I fill the void with before it starts sinking?”source ↗
Where this came up
People with this problem also raised
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- 31Should I use foam or caulk to seal gaps in exterior walls?