Will My Concrete Sink Again After Lifting?

Polyurethane foam fills the void completely and doesn't wash out or decompose, so the slab won't drop back into the same gap it came out of. The honest caveat: if there's an active water problem under the slab that isn't dealt with, erosion can carve a new void over time.

That's why we don't just pump and run. During every estimate we look at where water is coming from — a downspout dumping at the slab edge, poor grading, a low spot that pools — and flag it. Fix the lift and the drainage together and the repair holds for the life of the concrete. Void filling is often part of that, stabilizing the soil so a new gap doesn't form.