Building permits under the Building Act 2011
WA runs building approval under the Building Act 2011, with permits issued by your local government's permit authority. Applications come in two flavours: a certified application (BA1), where a private building surveyor has already checked compliance and the council has up to 10 business days to issue the permit, and an uncertified application (BA2) for smaller residential work, where the council does the checking and has up to 25 business days. Work that affects the structure of a house, and underpinning plainly does, generally needs a permit, while genuine like-for-like maintenance may not. The exemptions are specific and councils apply them case by case, so check with your local government or a private building surveyor before assuming your job is exempt. Most underpinning contractors arrange the permit; get the permit number before work starts, and keep the permit with the engineering documents when the job wraps up, because unauthorised structural work is expensive to regularise later and awkward at sale time. Our regulations hub compares WA with the other states.
Registered builder requirements
Building work in WA valued over $20,000 must be carried out by a registered building contractor. Registration sits with the Building Services Board, administered by Building and Energy, the state building regulator within WA's industry regulation department (see commerce.wa.gov.au). Since most underpinning jobs cost $10,000–$40,000, many WA foundation repairs cross the registration threshold, and any full restumping job at $15,000–$30,000 certainly does. Below $20,000 registration is not mandatory, which is exactly where you should be more careful, not less: an unregistered operator quoting $18,000 has fewer obligations and you have fewer remedies.
Home indemnity insurance
For residential building work over $20,000, the builder must take out home indemnity insurance in your name before accepting any money or starting on site. It protects you against losing your deposit or being left with incomplete or defective work if the builder dies, disappears or becomes insolvent. Ask for the certificate at contract stage and keep it with the permit paperwork, because the cover follows the property and matters to future buyers as well as to you. A builder who hedges on home indemnity insurance for a $30,000 job is not someone to hand a deposit to.
Engineering and owner-builders
Perth's sands are kinder to footings than eastern-states clay, but WA still has reactive pockets, fill sites and coastal limestone quirks, and underpinning should always be designed by a structural engineer rather than sized by a salesperson. Expect an engineer's report at $600–$1,200 and a soil test at $400–$1,000; permit authorities expect engineering documentation for structural work. Owner-builders get a brief mention because WA formalises them: to do your own building work over $20,000 you need owner-builder approval from the Building Services Board, and restrictions apply, including limits on selling the property within seven years unless you take out home indemnity insurance. For structural foundation work, owner-building rarely makes sense; our underpinning guide explains why this is specialist territory.
On any WA quote over $20,000, three items should be explicit: the builder's registration number, who is obtaining the building permit, and home indemnity insurance in your name before any money is paid.
Checking a registration
Building and Energy maintains a free online register of registered building service providers. Search the builder's name or registration number, confirm the registered entity matches the name on your contract, and check the registration is current. The regulator also publishes disciplinary outcomes, which are worth a scan for any firm quoting you five figures. If you are still gathering quotes, our Perth directory lists underpinning and foundation specialists, and our quote checklist helps you compare them on the same terms.
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Common questions
Do I need a building permit for underpinning in WA?
Generally yes, because underpinning affects the structure of the house. Permits are issued by your local government under the Building Act 2011. Limited exemptions exist for minor like-for-like repairs, so confirm your specific job with the council or a private building surveyor.
Does my contractor need to be a registered builder?
For building work over $20,000, yes: WA law requires a registered building contractor, registered with the Building Services Board. Under $20,000 registration is not mandatory, which makes checking references and engineering input even more important on smaller jobs.
When is home indemnity insurance required in WA?
For residential building work over $20,000. The builder must hold the policy in your name before taking any money or starting work, and you should receive the certificate at contract stage.
What is the difference between a BA1 and BA2 application?
A BA1 is a certified application, checked by a private building surveyor first, with a 10-business-day council turnaround. A BA2 is uncertified, checked by the council itself, and can take up to 25 business days. Your contractor or surveyor will advise which suits the job.