Geopolymer foam injection
Expanding geopolymer foam injected at depth to fill voids and re-level slabs and footings.
- UK-wide coverage and local knowledge
- 20 year remedial warranty
- Diagnostics to remedial work
What it is
Similar in principle to resin injection, geopolymer foam is engineered for larger void filling and slab re-levelling. It is lighter than resin and can be tuned for different soil profiles. It cures in minutes.
Foam systems are particularly good at filling voids beneath concrete slabs without adding significant weight to the underlying ground. That makes them the go-to method for sunken floors, settled drives, and conservatory bases.
Density is controllable from around 40 to 200 kg/m³ depending on the application, so the engineer can pick a foam stiff enough to carry the load without overloading already-weak ground.
When it's used
Foam injection is the right tool for settled internal slabs, sunken paths and driveways tied into the building, garage floors that have dropped at one corner, and conservatory or porch bases where the slab has parted company with the perimeter foundation. It also handles ground improvement under lightly loaded structures where adding the weight of resin or concrete to already-weak ground would make things worse. Most jobs are completed in a day, with the lifted area usable within an hour of the foam reaching working strength.
Density is controllable from around 40 to 200 kg per cubic metre depending on the application, so the engineer can pick a foam stiff enough to carry the load without overloading the ground beneath. This is the key difference from resin: foam is engineered to be light. That makes it the wrong tool for stiffening the load-bearing soil beneath a wall foundation, where resin or a structural method should be specified instead. The pattern we see most often is a homeowner asking for foam after a quote for traditional underpinning has scared them; sometimes it is genuinely the right call, sometimes it is the cheapest answer to the wrong question.
How the work runs
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1. Survey and grid
Affected area mapped, target depth set, ports drilled.
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2. Injection and lift
Foam delivered in measured doses, levels checked continuously.
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3. Make good
Ports filled, finishes restored.
Pros and cons
Pros
- Excellent for slab re-levelling
- Adds minimal weight to underlying ground
- Quick, most jobs complete in a day
- Can be used inside a property without major disruption
- Cures within an hour to working strength
Cons
- Lower compressive strength than resin or concrete
- Not a structural repair for failing wall foundations
- Best for slabs and shallow voids, not deep subsidence
How it compares
Every method we offer at a glance.
| Method | Time on site | Reaches | Disruption | Best for |
|---|---|---|---|---|
| Beam and base | 2 to 6 weeks | Up to 4m via deeper bases | High, large pits with significant excavation | Variable ground, bay windows, redistributing loads |
| Foam injection | 1 day for most jobs | Treats soil and slabs to 3m | Minimal, drilled ports only | Slab re-levelling, void fill, conservatory bases |
| Mass concrete | 2 to 6 weeks per elevation | Up to 3m hand-dug | High, open excavation and significant spoil | Shallow failures on traditional ground, insurance claims |
| Mini piled | 1 to 3 weeks on site | 10–15m, sometimes more | Medium, compact rigs and internal floor lifts | Deep bearing layers, made-up ground, restricted access |
| Resin injection | 1 day for most jobs | Treats soil to 3–4m via ports | Minimal, small ports and no spoil | Granular soils, intact foundations, voids and density loss |
| Screw pile | 2 to 5 days | 5–10m typical | Low, no excavation and no concrete cure | Lighter loads, time-critical jobs, conservatories |
Suitability
Copes well with slab re-levelling, void filling, and ground improvement under lightly loaded structures. Struggles with structural wall failures, heavy loads, and deep-seated clay shrinkage. The diagnostic question is whether the failure is in the slab or in the wall foundation. Slab problems are foam's home territory; wall foundation problems need a structural method.
Common questions
Get a free assessment
A surveyor will be in touch within 48 hours.