Underpinning & restumping firms in Sydney

Foundation repair in Sydney

Cumberland Plain clay moves enough to keep underpinners busy from Liverpool to Rouse Hill, while older stumped stock clusters in the inner west and the mountains. Two minutes with the terminology guide tells you which trade to call; the subsidence signs guide tells you whether to call anyone at all.

Restumping or underpinning: which one do you need in Sydney?

The symptom tells you which trade to call. Sloping or bouncy floors, doors and windows sticking, and gaps opening between floor and skirting point to failed stumps under a timber-framed house: that is restumping (reblocking in Victoria). Stepped cracks in brickwork, cracks that widen with the seasons, and a slab home pulling away from its footings point to footing movement: that is underpinning. Our guides on the signs of failed stumps and the signs of subsidence walk through each, and restumping vs reblocking vs underpinning settles the terminology.

In Sydney, both trades work the same suburbs: Cumberland Plain clay keeps underpinners busy from Liverpool to Rouse Hill, while stumped Federation weatherboards cluster in the inner west and the mountains. Get the diagnosis right before the quotes, or you will get three different diagnoses instead of three comparable prices.

Permits, licences and insurance in NSW

When approval is needed. NSW planning law sorts small residential projects into exempt development (no approval), complying development (fast-track certificate) and development needing a full council DA. Genuine like-for-like maintenance and minor repairs generally sit in the exempt category. Underpinning is a harder case: because it alters the structural support of the building, it typically cannot be waved through as simple maintenance, and most jobs proceed with approval, either through a council development application or, where the work qualifies, a complying development certificate issued by council or a registered private certifier. The boundaries depend on your property, the zoning and whether heritage controls apply, so the honest advice is to check with your council or a private certifier before work starts rather than rely on a contractor's assurance that "no one bothers with approval for this". Our regulations hub compares each state's approach.

Contractor licensing. Residential building work in NSW worth more than $5,000 (labour and materials) must be done by the holder of a contractor licence, regulated by Building Commission NSW alongside NSW Fair Trading. Since most underpinning jobs land between $10,000 and $40,000, every quote you receive should come from a licensed contractor, and the licence number should appear on the quote and the contract. Contract rules scale with value: work over $5,000 needs a written contract with prescribed terms, and work over $20,000 needs a full home building contract with a progress payment schedule. A contractor who wants a big job done on a handshake is exposing you, not saving you paperwork. Licensed work also carries statutory warranties under the Home Building Act, including that the work will be done with due care and skill and comply with the plans, which is a legal backstop you simply do not have with an unlicensed operator.

Home Building Compensation cover. Where the contract price is more than $20,000 including labour and materials, the contractor must take out Home Building Compensation (HBC) cover, run through the state insurer icare, before taking your deposit or starting work. HBC protects you if the builder dies, disappears or becomes insolvent and cannot finish or fix the job. You should be given a certificate of cover naming your property; keep it with the contract. A significant share of underpinning quotes cross the $20,000 line, so ask about HBC at quote stage.

Engineering sign-off. Underpinning in NSW is engineer-led by convention as much as by regulation. A structural or geotechnical engineer should diagnose the movement, design the fix and, ideally, inspect at key stages, with an engineer's report typically costing $600-$1,200 and design work up to $2,500. Where the job goes through an approval pathway, the certifier will expect engineering documentation, and your insurer may ask for it too if the damage becomes a claim. Before committing to any method, it is worth confirming whether you need underpinning at all: plenty of cracked NSW homes are moving seasonally rather than failing, and our underpinning guide explains the difference.

Full detail, including the checklist: the NSW rules explained.

What it costs in Sydney

Underpinning dominates Sydney quotes: $10,000 to $40,000 for typical residential jobs, priced per metre, per pile or per zone depending on method. Stumped houses follow the national restumping ranges.

Full breakdowns: restumping costs, underpinning costs, when a partial restump is enough.

Getting quotes you can compare

A quote you can compare states the method, the extent (number of stumps, or metres, piles or zones for underpinning), the stump material, size and founding depth or the depth to bearing, who obtains the permit and whether its cost is included, the insurance that applies, what happens to cracks afterwards, and the warranty in writing. A number produced in the driveway without a look under the floor or an engineer's report is a guess, and the cheapest guess is the one that costs you later.

• Which licence or registration do you hold, and can I check it on the register?
• Is the permit your responsibility, and is it in this price?
• What stump material, size and founding depth are you quoting, and why?
• Have you priced against the engineer's report, or your own diagnosis?
• What is the warranty, and what insurance sits behind it if you close down?
• How many days on site, and will the house be habitable throughout?

More in choosing a contractor and what the process looks like.