If you’ve been researching custom home builders in Brisbane, you’ve probably seen ‘fixed price’ used as a selling point by almost everyone. And right now, with construction costs climbing and plenty of uncertainty in the air, it’s one of the first questions we hear from people considering a build:
‘Does a fixed price building contract actually mean my price won’t change?’
It’s an important question when you’re investing $800K+ into a home that’s supposed to be unmistakably yours. The honest answer is: it depends on what’s in the contract. ‘Fixed price’ can mean genuine protection, or it can mean very little, depending on how the document behind it is written and how much work the builder did before asking you to sign.
What a fixed price contract really means
A fixed price building contract, sometimes called a lump sum contract, sets the total cost of building your home at the time of signing. Once that contract is executed, your builder absorbs any cost increases that arise during construction. Those increases don’t come back to you. In Queensland, residential builds typically use one of three standard fixed price contracts:
- HIA
- Master Builders Queensland
- QBCC.
All three operate on this same principle, and under the QBCC Act 1991, the circumstances in which a builder can legitimately increase a contracted price are tightly defined.
That matters right now. Building costs across Brisbane have been rising. Industry forecaster Rider Levett Bucknall projects around 5% construction cost growth in Brisbane for 2026, among the higher rates in the country, partly due to the Olympic infrastructure pipeline drawing on the same labour and materials pool as residential builds. For anyone who has already signed a fixed price contract with a stable, well-resourced builder, those pressures stay firmly on the builder’s side of the ledger.
The key phrase here is ‘already signed’, which brings us to what can still move the price, even on a fixed price contract.
