If a structural engineer has used the word underpinning, the conversation tends to skip straight to mass concrete. That is the textbook answer, well understood and broadly accepted by insurers. It is also slow, dirty, and often more invasive than the problem deserves. Modern foundation engineering has a wider toolbox than the textbooks of thirty years ago, and a competent specialist will consider all of it before defaulting to concrete.
Resin injection
Resin injection treats the soil rather than the foundation. Geopolymer resin expands beneath the foundation, densifies granular ground, fills voids, and often re-levels minor settlement. Best for sandy or silty soils that have lost density. Wrong for clay shrinkage and wrong where the foundation itself has failed.
Screw piles
Helical steel piles wound into the ground by hydraulic torque. No vibration, no spoil, immediate load capacity. Increasingly the default for new extensions and conservatories on tricky ground. Can be used as remedial underpinning where access allows, but more often used preventatively.
Mini piles
Small-diameter piles (typically 150–300mm) installed by compact rigs that fit inside basements or rear gardens. The right answer when the bearing layer is many metres down or where mass concrete would require dangerous depth excavation. More expensive per metre than mass concrete but often cheaper overall once depth and shoring are accounted for.
Beam and base
Beam and base is a reinforced concrete beam threaded through or built against the existing wall, supported on bases or piles. Spreads load over a longer run than traditional pin underpinning and works well for long elevations and weak existing footings.
Geopolymer foam re-levelling
A sub-set of resin injection focused on slabs rather than walls. Expands beneath a settled concrete slab and lifts it back to level without breaking it out. Ideal for garage floors, conservatory bases, and industrial slabs.
Tree root management
Sometimes the cheapest and most effective intervention is not underpinning at all, it is removing or reducing the tree that is drying the clay. Done with arborist input and proper monitoring (because removal can also cause heave), it can stabilise a property for a fraction of the cost of structural work.
How to choose
The right answer depends on the soil, the depth of failure, the building's tolerance for disruption, the engineer's design, and the homeowner's budget and timeline. A properly scoped diagnostic survey looks at all of these together. If a quote arrives without that scoping, it is a price for a method, not a price for a solution. The full scoping sequence is on our process page.