Illegal Building Work Disclosure Obligations

Illegal or unauthorised building work refers to renovations, extensions, decks, sheds, pools or other structures built without the required council approval, building permit or final inspection sign-off. It is more common than many buyers expect, particularly with owner-built additions, older properties that have changed hands several times, and work carried out by unlicensed operators. Understanding who is responsible for disclosing it, and what your options are if it turns up during a sale, matters for both buyers and sellers.

What Counts as Illegal or Unauthorised Building Work

Work can be unauthorised for several reasons: no permit was ever obtained, the work departed from an approved plan, a licensed tradesperson was never engaged for work that legally requires one, such as electrical or plumbing work, or the project was never signed off with a final inspection certificate. Structural additions like carports, granny flats, retaining walls and pools are common culprits, since owners sometimes treat these as minor projects rather than works requiring formal approval.

How It Gets Discovered

Unauthorised work often surfaces during a building and pest inspection, when council records are checked as part of due diligence, or when a buyer's conveyancer notices that a structure shown in photos or on a plan does not match what council has on file. Council property certificates, which your conveyancer orders as a standard part of the search process, will often reveal outstanding notices, orders, or a lack of approval for structures that are clearly visible on site. Neighbours reporting suspected unauthorised work to council is another common trigger, sometimes years after the work was actually completed.

A Seller's Disclosure Obligations

Disclosure requirements around known defects and illegal work vary by state, but sellers generally have an obligation not to actively conceal a known issue, and in some states there are specific statutory disclosure requirements that apply to the contract of sale itself. A seller who knowingly hides unauthorised work, or misrepresents its status, risks the buyer later seeking remedies against them, including in some circumstances a claim for compensation or, in serious cases, contract rescission. This is general information rather than legal advice, and sellers with a known compliance issue should get advice from their conveyancer or solicitor before listing a residential sale.

What It Means for a Buyer

For a buyer, unauthorised work creates a few practical risks: council may eventually require the work to be brought up to standard, removed, or formally approved retrospectively, and any of these outcomes can involve cost and delay. It can also affect insurance, since some insurers will decline or limit cover for damage connected to unpermitted structures. None of this necessarily means you should walk away from a purchase, but it does mean the issue needs to be priced in, addressed contractually, or resolved before you commit. A buyer who proceeds with full knowledge of the issue is in a very different position from one who finds out only after settlement, which is exactly why disclosure and due diligence both matter here.

Insurance, Finance and Resale Implications

Lenders occasionally raise questions about unauthorised structures during the valuation process, particularly where they add significant floor area, and this can affect finance approval timing. At resale, an unresolved compliance issue tends to resurface with the next buyer's inspection, so leaving it unaddressed does not make the problem disappear, it simply defers it to a future transaction, usually at greater cost than dealing with it now. Building regulators such as Queensland's QBCC take a firm approach to unlicensed work, as outlined in its guidance on unlicensed building work and consumer risk, and equivalent regulators exist in every other state.

How This Differs Across States

The regulator and terminology involved differ from state to state, with building certifiers, private certifiers or council building surveyors playing the front-line compliance role depending on where the property is located. Some states run periodic audit or amnesty style programs that allow owners to regularise older, minor unauthorised work without the same scrutiny applied to a fresh application, while others expect every non-compliant structure to go through the full assessment process regardless of its age. A conveyancer familiar with the local regulator's approach, whether you are buying in Queensland or elsewhere, can give a more realistic picture of how straightforward, or how involved, a retrospective approval is likely to be for a specific property.

Options If You Have Already Bought

If unauthorised work is discovered after settlement, options include applying to council for retrospective approval, which may require an engineer's report or upgrades to meet current standards, negotiating with the previous owner if misrepresentation can be shown, or simply managing the risk by disclosing it honestly when you eventually sell. Getting a clear picture of what council actually requires, rather than guessing, is the first step, and a building surveyor or certifier can advise on what a retrospective approval pathway would involve. In some cases the more practical outcome is removing a minor unauthorised structure entirely, rather than pursuing an approval that may not be granted.

How a Conveyancer Manages This

Before you exchange on a purchase, your conveyancer's review of council certificates and contract disclosures is your main opportunity to identify a compliance issue and negotiate around it, whether that means a price adjustment, a special condition requiring the seller to resolve it, or simply proceeding with clear knowledge of what you are taking on. This matters just as much for a straightforward residential purchase as it does for a subdivision project, where compliance history can affect what further development is possible.