What counts as a variation
The QBCC defines variations as changes made to the contract after it is signed, such as changes to the materials used or the work performed. It calls undocumented variations a frequent cause of budget blow-outs and building disputes.
NSW separates an addition, something you think of after signing and want added, from a variation, a change to what was already agreed. A builder may need a variation because of a council requirement or something unforeseen, but if the variation is needed because of the builder’s fault, you do not have to pay for the extra work to fix it.
In Victoria, variations are changes that you or the builder want, or that the building surveyor orders after the contract is signed and building has started.
What the written variation should show
The QBCC lists the details a variation document must include. Here they are as a blank form, the way you would check one line by line.
- A description of the variation
- The date of the request for the variation
- If it will delay the work, the contractor’s reasonable estimate of the delay
- The change to the contract price, or how it will be calculated, and the date an increase is to be paid or a decrease credited
NSW asks for more on the price: documents authorising a variation must explain its cost and its effect on the overall contract price, and should show how the change was calculated rather than give a bare dollar figure. Before the varied work starts, NSW says the builder should give you a written description, any plans or specifications, and the extra cost and time, and you should both sign if you agree.
The order of events in Queensland
- You and the contractor agree on a change.
- The contractor puts it in writing. They must give it to you in person, by post or by email, before the varied work starts or within five business days of agreeing, whichever comes first.
- You reply in writing. You must also respond in writing to say whether you agree to the variation work.
- Keep the record. The QBCC calls storing variation records essential in case you need evidence to make a claim.
When it is urgent
The Queensland exception is work that must be done urgently where writing it up first is not reasonably practicable, for example for safety. NSW has a similar exception where there is likely danger to someone or damage to property: the written variation may then be done after the work.
The insurance follows
When a variation alters the project’s value, it is the contractor’s job to update the Queensland home warranty cover, though you may need to sign some documents.
Victoria’s rules on variations
By law, you and your builder must agree to a change in writing, and put the details, including the new price and completion date, into your contract before the builder does the work. That change is made with a variation notice.
- The small-change exception. No variation notice is needed when the builder reasonably believes the change will not require any change to the project’s permits, will not cause delay, and will not add more than 2% to the original contract price.
- Surveyor-ordered changes. The builder must give you copies of the order and the variation notice. If you do not agree, you must tell the builder in writing within five business days of receiving the notice.
- Problems the builder should have foreseen. You should not have to pay for variations to deal with issues the builder should have identified before starting, such as rock that could have been predicted from the foundation data.
Victoria passed new building contract laws in September 2025 that take effect by 1 December 2026 and may change the variation process in this section. Until then, Consumer Affairs Victoria says the current laws remain the same. Check Consumer Affairs Victoria before you sign.
For Victorian building permits issued from 1 July 2019, if variations push the revised final cost of work up by $15,625 or more, you must tell the BPC within 28 days of finding out, and you may have to pay a penalty levy if you do not.
Prime cost items and provisional sums
Some price changes come from allowances written into the contract rather than from variations. NSW describes prime cost items as fixtures, such as a stove or special fittings, chosen after signing, which cannot be costed exactly before work begins; the builder should allow a price that covers their expected cost.
In Victoria, the contract must include a detailed list of prime cost and provisional sum items with a breakdown of the estimate for each, and the builder must give you a copy of any invoice or receipt showing what each one cost them, as soon as possible after they receive it. Consumer Affairs Victoria’s advice is to avoid these items where you can, by putting the make, model, colour and style of your selections into the contract.