Void beneath slab A void beneath a slab is an empty space between the concrete and the supporting soil or base material. The loss of contact reduces the slab's ability to distribute loads evenly.
Voids may develop because of erosion, settlement, soil shrinkage, or underground utility activity. Unsupported concrete is more vulnerable to cracking, rocking, and eventual failure under repeated loading. Repair methods depend on the size of the void and its underlying cause.
Frequently Asked Questions About Void beneath slab
What is a void beneath a slab?
An empty space between the concrete and the soil or base beneath it, so the slab no longer bears evenly on its support.
What creates voids?
Erosion, settlement, soil shrinkage and underground utility activity.
Why are voids dangerous?
Unsupported concrete flexes under load, which leads to cracking, rocking and sudden failure, sometimes without prior warning at the surface.
How are voids repaired?
Small voids may be filled and compacted; larger ones typically require removing the slab, rebuilding the base and repouring.