Underpinning a subsiding home: diagnosis before repair

What underpinning actually involves

Underpinning stabilises footings that have subsided, restoring support beneath a section of a home that's dropped. Traditional concrete underpinning excavates beneath the existing footing and pours new piers to a stable depth, priced per pier. Resin injection is the newer alternative — a structural resin injected into the ground to firm it up, priced by the treated area and suited to smaller corrections with far less excavation.

Neither method should begin without investigation. A geotechnical report and a structural engineer's design typically come first, identifying why the ground moved and specifying exactly what's needed — because getting the diagnosis wrong means underpinning a house whose real problem is a leaking drain or a tree drawing moisture from the soil. That upfront assessment is essential, not optional.

How the cost works

Underpinning is a significant project, priced either per pier for traditional concrete work or by the treated area for resin injection. A single affected section of a home is a substantial sum, and multiple sections or a whole side climb well beyond that. Individual piers are priced each, so the number of them drives the concrete-method total.

The investigation stage adds cost before any repair — a geotechnical report and engineer's design are a few thousand dollars, and they are money well spent because they stop you fixing the wrong thing. Access, soil type and depth to stable ground all move the price. Treat every figure as indicative; underpinning is quoted only after assessment, and any contractor quoting without one is a warning sign.

Choosing a specialist

Underpinning is structural work, and licensing is state-dependent — the contractor typically needs a builder's or specialist licence, and the design should come from a qualified structural engineer regardless of state. Insist on the engineer's involvement: their design is what makes the repair sound and what a certifier and your insurer will look for.

Because this is high-stakes work, check the contractor's experience with your specific method and soil, their insurance, and the warranty on the work — reputable underpinning carries a meaningful guarantee. A good specialist won't quote off a phone call; they'll want the geotechnical and engineering input first, and they'll be upfront that fixing the underlying cause, like drainage, is part of a lasting repair rather than an upsell.

Mistakes to avoid

Underpinning goes wrong when people skip the diagnosis, chase the cheapest quote for structural work, or treat the symptom and ignore the cause. Each mistake risks paying twice — once for the underpinning and again when the movement returns.

• Accepting a quote to underpin without a geotechnical report and engineer's design
• Fixing the cracking without addressing the cause, like drainage or a nearby tree
• Choosing the cheapest contractor for structural work that has to last decades
• Not confirming the structural engineer's design and certification are included
• Overlooking the contractor's licence and insurance for structural work in your state
• Skipping the warranty conversation on a repair this significant