Application
Void filling and slab stabilization
Sometimes a slab hasn’t dropped much yet but is unsupported. Filling voids beneath it with polyurethane can restore contact with the ground and reduce the risk of cracking under load.
Why it settles
- Washout from downspouts, irrigation or leaks
- Settlement of loose fill
- Erosion along slab edges
Often suitable
- Hollow-sounding slabs
- Visible gaps along slab edges
- Slabs that rock or move under load
Usually not suitable
- Active sinkholes or large cavities from broken sewer lines — fix the cause first
- Areas with ongoing water flow beneath the slab
Risks, drainage and other considerations
- Identify and repair the water source
- Very large voids may need other fill methods
- Buried utilities must be located
Lift or replace?
Lifting keeps the existing concrete, so it makes sense only when that concrete is worth keeping. If it is broken up, deteriorated or heaved, replacement is usually the better route. See lifting vs replacement and what affects cost.
Check before you ask
Use the free slab self-check, the area calculator or the photo checklist, then send the summary with your request. See also the visual guides.
Questions
How do I know there’s a void?
Hollow sounds when tapped, gaps along edges or slabs that rock are common signs. A contractor can confirm by probing.
Request an assessment
Other applications
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