Guide
What is polyjacking?
Polyjacking — also called polyurethane concrete lifting or foam jacking — raises and supports settled concrete by injecting an expanding two-part polyurethane beneath the slab through small drilled holes.
The short answer
When soil under a slab settles or washes away, the slab loses support and drops. Polyjacking fills that space with foam that expands and hardens, supporting the slab and, when injected in controlled stages, lifting it back toward level.
How it works
- The slab is assessed and the cause of settlement identified
- Small holes are drilled through the concrete
- Foam is injected in stages while the slab is monitored
- Holes are patched and joints are usually sealed
Good candidates
- Slabs that have settled as a unit and remain largely intact
- Slabs with voids beneath them
- Trip edges and slabs sloping toward buildings
Not good candidates
- Shattered, crumbling or heavily deteriorated concrete
- Slabs that have heaved upward
- Settlement caused by an ongoing problem (a leaking pipe, active erosion) that hasn’t been fixed
Risks and limitations
- Existing cracks usually remain visible
- Over-injection can crack a slab or lift it unevenly — experience matters
- Foam can migrate into drains or voids if not controlled
- Without fixing drainage, settlement may recur
Next step: an assessment
Photos help, but the only reliable way to decide whether a slab can be lifted is an on-site look at the concrete, the drainage and the likely cause of settlement. Submit a request and the HAUSE intake team will review it and confirm whether a suitable contractor is available in your area.
Conceptual illustration
What happens under a settled slab
Water and loose fill leave a void; foam injected through small holes fills it and lifts the slab.
1 · Void forms
Water, erosion or poorly compacted fill leaves a gap under part of the slab.
2 · Slab drops
Unsupported concrete sinks, creating trip edges and slope toward the house.
3 · Small holes
The contractor drills small injection holes at planned points.
4 · Foam fills & lifts
Expanding polyurethane fills the void and raises the slab in controlled steps.
Text version
- 1 · Void forms: Water, erosion or poorly compacted fill leaves a gap under part of the slab.
- 2 · Slab drops: Unsupported concrete sinks, creating trip edges and slope toward the house.
- 3 · Small holes: The contractor drills small injection holes at planned points.
- 4 · Foam fills & lifts: Expanding polyurethane fills the void and raises the slab in controlled steps.
More in the visual guides · try the slab self-check.
Questions
How long does lifted concrete stay level?
It depends on why it settled. If the cause (usually water or loose fill) is addressed, results can be long-lasting; if not, movement can recur. Ask any contractor what they will do about the cause.
Can I use it right away?
Return-to-use depends on the foam product, temperature and site conditions. Your contractor should confirm.
Have a settled slab?
Describe it, add photos if you have them, and the HAUSE intake team will review your request and confirm whether a suitable contractor is available near you.
Request an assessment