How to choose a granny flat builder in Queensland

1. The licence

Building work in Queensland is regulated by the Queensland Building and Construction Commission (QBCC). Before you sign anything:

• Find the builder on the QBCC licence register using the licence number.
• Check the licence class covers your type of work, and that the name on the quote and contract is the entity that holds the licence.
• Check for any history of directions, orders or disciplinary action.
• Remember advertising for building work over $3,300 must show the licensee's QBCC licence number. A missing number is a red flag.
• Plumbing and drainage work needs licensed plumbers or drainers; for plumbing work the licence number must be shown regardless of value.

2. The contract

In Queensland, residential building work over $3,300 needs a written contract. The QBCC publishes regulated domestic building contracts for free, so you don't need to accept a builder's own paper blindly. Have a construction lawyer read it: an hour of their time is among the best-value money on a project this size. Use this list:

• Is the contracting entity the one that holds the licence?
• Is the price inclusive of GST?
• Which items are provisional sums or prime cost allowances, and what happens when they are exceeded?
• Read the exclusions list line by line: it is the most important page in the document.
• Is the payment schedule stage-based rather than front-loaded?
• Must variations be in writing, priced and signed before the work is done?
• Who carries the risk of rock and unexpected ground conditions?
• Who obtains planning, building, plumbing and water authority approvals, and who pays the fees?
• Who pays council infrastructure charges, and are they inside the price?
• How is practical completion defined and how are defects rectified?
• What are the termination grounds, and what happens to money already paid?

3. The deposit

The QBCC's guidance for licensees and homeowners states the maximum deposit is 10% on contracts under $20,000 and 5% on contracts of $20,000 and above. That is a legal cap, not a recommended amount, and it's worth adding up everything payable before work starts: a deposit at the cap plus a separate "commencement fee" on the same day can breach it in combination. Money paid above the cap is harder to recover if the builder fails.

4. Home warranty insurance

Most residential building work in Queensland valued at more than $3,300 (including materials, labour and GST) must be insured through the Queensland Home Warranty Scheme. It protects owners if a licensed contractor fails to complete the work or fix defective work. According to the QBCC's consumer guide it covers structural defects for up to six years and non-structural defects for one year, where a licensed contractor has done the work under a contract. Your contractor arranges the cover on your behalf (ask how the premium is charged), and cover starts from the earliest of the premium being paid, the contract being signed or work starting.

Ask to see the notice of cover for your job, in your name, before you pay a deposit. It is the sharpest single test, and it costs you one sentence.

5. The certifier

A building certifier assesses your building application, decides whether to issue a building approval, inspects the work and certifies it. They're licensed by the QBCC and can work for council or in private practice. In most cases your builder engages the private certifier for you, but your contract should say who is responsible. A certifier checks that construction matches the approved plans and building standards. They do not supervise the quality of the builder's work, so don't treat certification as a substitute for checking the builder. You can check a certifier's licence on the QBCC register too.

6. Financial health and reputation

• ABN and ACN active, and registration dates consistent with the claimed trading history
• Company not in external administration; no insolvency notices under the name
• Directors not associated with wound-up companies
• Reviews consistent across independent platforms, not only the builder's own site
• Two or three recent Queensland clients you can speak to, ideally with a finished secondary dwelling

A very new company trading under an established name can be an ordinary restructure. It can also be a pattern where a business fails and reappears with the same brand. Neither is proof of anything, but both are a reason to ask.

Questions to ask every builder

1. "What is your QBCC licence number, and which entity will sign the contract?"
2. "Can I see the home warranty notice of cover before I pay a deposit?"
3. "What is excluded from your price, and which items are provisional sums?"
4. "Who engages the certifier and pays for approvals and inspections?"
5. "Have you built a secondary dwelling in my council area, and did it need a planning application?"
6. "What happens if you hit rock or poor soil?"

Sources

• QBCC, Key information for QBCC licensees and homeowners (May 2025): deposit caps, advertising and licence number rules.
• QBCC, Role and responsibilities of a certifier.
• QBCC, Queensland Home Warranty Scheme and Consumer Building Guide ($3,300 threshold; warranty periods).
• Toowoomba Regional Council, Building certifiers (what certifiers do and don't do).

General information only, not legal or building advice. Confirm current requirements on the QBCC website and with a construction lawyer before you sign.

Frequently asked questions

How do I check a builder in Queensland?

Search the QBCC licence register for the builder's licence number, check the licence class covers your work, and check for any history. Residential building work over $3,300 must be done under a written contract and be covered by home warranty insurance through a licensed contractor, so also ask for the notice of cover.

How much deposit can a builder ask for in Queensland?

The QBCC's guidance for licensees and homeowners gives a maximum of 10% for contracts under $20,000 and 5% for contracts of $20,000 and above. Don't pay more, and add up everything payable before work starts.

What does the Queensland Home Warranty Scheme cover?

It protects owners if a contractor fails to complete residential building work or to rectify defective work, where the work is insured under the scheme. The QBCC's consumer guide describes up to six years for structural defects and one year for non-structural defects, provided a licensed contractor did the work under a regulated contract.

Who engages the building certifier?

In most cases your builder engages the private certifier on your behalf, but your contract should say who is responsible. Certifiers are licensed by the QBCC, can work for council or privately, and check that building work meets the approved plans and building standards. They do not supervise the quality of the builder's work.

What should be in a granny flat building contract?

Price including GST, a clear scope and exclusions list, provisional sums and what happens when they're exceeded, a stage-based payment schedule, how variations are approved in writing, who obtains approvals and pays fees, who carries ground-condition risk, the defects process and the termination terms.

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