How to choose a remedial or underpinning contractor

The hiring checks that matter, from licensing and engineering to how a quote should be written, so you back the right contractor for a structural job.

Underpinning and concrete cancer repair are among the higher-stakes jobs a homeowner commissions: they are structural, expensive, and hard to put right if done badly. The good news is that a short due-diligence list separates a reliable remedial contractor from a risky one. Do that work early, not after signing.

Licensing and insurance

Structural and underpinning work is regulated building work in every state, so the contractor should hold the appropriate builder or trade licence for structural work. Use your state regulator, for example NSW Fair Trading or the Victorian Building Authority, as the source for licence status. Ask for current public liability insurance and, where the job size requires it, home warranty or builder's warranty insurance.

Engineering and method

For any structural movement, the repair should be based on an independent structural engineer's diagnosis and design, not just the contractor's opinion. Ask who is providing the engineering and whether the underpinning will be designed and certified by a qualified engineer. A contractor confident in their work will welcome an engineer's involvement; one who dismisses it is a warning sign. Make sure the proposed method actually matches your problem, and if two contractors propose different methods, ask each to explain why theirs suits your soil and footing.

How the quote should read

A good quote is specific. It should state the method, the number of piers or injection points, the design load, what is and is not included, how the site will be reinstated, and what monitoring or guarantee follows. Be cautious of quotes given without a site inspection, prices far below the others, pressure to decide on the spot, or large up-front deposits. Ask for references or recent local examples of the same kind of work, and get the scope in writing.

Finally, get more than one quote, but compare them on substance rather than price alone. The cheapest quote that skips the engineering, or a concrete repair that ignores waterproofing, is the one most likely to cost you again.

Questions to ask before you hire

Ask these directly, in writing if you can, before you sign anything:

• What is your current licence number, and for which class of work?
• Who is the structural engineer designing and certifying this job, and can I see their qualifications?
• What method are you proposing, and why does it suit my soil and footings specifically?
• What is included in the price, and what could add to it once you start digging?
• What happens if you find something different once excavation begins?
• What warranty or guarantee applies to the completed work, and for how long?
• Can you provide references or addresses of similar recent jobs?
• What is your payment schedule, and how much is due before work starts?

Red flags: signs to walk away

In Queensland, unlicensed contracting on work valued over $3,300 is illegal, and QBCC's public register lets you check a licence number and any disciplinary history before you sign anything. NSW Fair Trading runs an equivalent home building licence check, and both regulators, along with the ACCC's Scamwatch service, publish the same recurring warning signs for building and renovation scams. Treat any of the following as a reason to get a second opinion, not a reason to panic:

• Refuses to give a licence number, or the number does not check out on your state regulator's public register.
• Quotes a price without ever inspecting the property.
• Wants a large deposit, half the job cost or more, before any work starts.
• Pressures you to sign on the spot, or offers a discount only if you decide today.
• Turned up unsolicited, door-to-door or after a storm, rather than being sought out by you.
• Recommends underpinning or major structural work without an independent engineer's report backing the diagnosis.
• Gives a verbal quote only, or a written quote that is vague about method, pier count or inclusions.
• Has no fixed business address, or reviews and references you cannot verify independently.

If you see two or more of these, get a second opinion from an independent structural engineer.

Common questions

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