Variations are the number one cause of cost blow-outs in Australian residential building projects. A variation is any change to the original scope, specification, or plan — and building contracts typically give builders broad rights to request and charge for variations, sometimes at rates significantly higher than the original contract price. Homeowners frequently report final costs 20-40% above the contract price, with variations cited as the primary driver. The problem is compounded by the fact that many variations arise from issues the builder should have foreseen — site conditions, compliance requirements, or design ambiguities — but didn't price into the original quote. A well-drafted variation clause protects you from absorbing the cost of the builder's errors and omissions.
What is a Variation Clause?
A variation clause in a building contract sets out the process for changing the scope, quality, or quantity of work from what was originally agreed. Variations can be initiated by the owner (wanting changes), the builder (identifying additional work needed), or required by law (compliance with building codes or council requirements). The clause typically covers how variations must be requested, approved, priced, and documented.
Red flags to watch for
Any clause allowing the builder to carry out variation work without your prior written consent removes your ability to control costs. You may receive invoices for work you never agreed to.
Without a reference point, the builder can charge premium rates for variation work. Variations should be priced using the same rates as the original contract wherever possible.
Without a cap, variations can push the final cost far beyond your budget. Some contracts include a clause allowing termination if variations exceed a specified percentage (typically 10-15%).
If the builder underquoted, missed something in the plans, or failed to identify a site issue they should have found during inspection, the cost of correcting their mistake should not be passed to you.
You should receive a detailed breakdown showing quantities, rates, and total cost for each variation before approving it. Lump sum variation quotes with no detail prevent you from assessing reasonableness.
Builders sometimes use minor variations to claim significant time extensions, delaying completion without genuine justification.
Your legal rights
Building contract variations in Australia are regulated by state and territory legislation. The Domestic Building Contracts Act 1995 (Vic) requires that variations over $500 be in writing and signed by the owner before work begins (s.38). The Home Building Act 1989 (NSW) provides that variations must be documented and agreed in writing. The Queensland Building and Construction Commission Act 1991 and the Building Industry Fairness (Security of Payment) Act 2017 (Qld) require written variation agreements. The Building Work Contractors Act 1995 (SA) imposes similar requirements. Under the Australian Consumer Law (Schedule 2 of the Competition and Consumer Act 2010), unfair contract terms in standard form building contracts may be void. State building authorities (VBA in Victoria, NSW Fair Trading, QBCC in Queensland) provide dispute resolution for variation disputes, and VCAT, NCAT, and QCAT respectively handle building disputes that cannot be resolved through mediation.
Questions to ask before you sign
- 1Does the contract require my written approval before any variation work can begin?
- 2How are variations priced — is there a schedule of rates, and does it apply to variation work?
- 3Is there a cap on total variation costs, and can I terminate if variations exceed a certain percentage?
- 4Who bears the cost of variations caused by the builder's errors, omissions, or failure to identify site conditions?
- 5What information must a variation quote include before I'm asked to approve it?
- 6How do variations affect the completion date, and is there a separate assessment of time impact for each variation?
Disclaimer: This guide is for educational purposes only and does not constitute legal advice. Contract law varies by jurisdiction and individual circumstances. Always consult a qualified legal professional before making decisions based on this information.