INSIGHT · CONTRACTS & PAYMENTS

One variation, five state rules:
who signs, what it states, when work can start.

9 October 2026

The home building Acts of NSW, Victoria, Queensland, South Australia and Western Australia each deal with variations to a residential building contract, and they do not say the same thing. NSW's Act makes each contract it covers include a term (s 7E; Schedule 2, Part 1, clause 1(2)) that any agreement to vary must be in writing signed by or on behalf of each party. Victoria bars a builder from giving effect to a variation without the owner's signed consent or signed request, with narrow exceptions. Queensland bars work on a variation before the owner agrees in writing. WA requires the owner to have a signed copy before the varied work commences.

People reviewing a set of architectural plans spread on a table

Analysed 9 October 2026 · Home Building Act 1989 (NSW), current version from 10 June 2026 · Domestic Building Contracts Act 1995 (Vic), Authorised Version 094 as at 1 July 2026 · QBCC Act 1991 (Qld), current version from 1 February 2026 · Building Work Contractors Act 1995 (SA), current version, and Regulations 2026 · Home Building Contracts Act 1991 (WA), as at 5 April 2023 · all read 9 October 2026, the NSW and SA registers through a rendering proxy because the sites block automated access.

Key takeaways

The signature rule differs: NSW: in writing signed by or on behalf of each party (Home Building Act 1989, Schedule 2, Part 1, clause 1(2)). Victoria: the owner's signed consent or signed request, attached to the builder's notice (Domestic Building Contracts Act 1995, ss 37 and 38). WA: in writing, signed by the builder and the owner or their agents (Home Building Contracts Act 1991, s 7).
The timing rule differs: Queensland: no work on the variation before the owner agrees in writing, and a written copy within 5 business days of agreement or before the work starts, whichever is first (QBCC Act 1991, Schedule 1B, s 40). WA: the signed copy goes to the owner before the varied work is commenced (s 7(2)).
Victoria and Queensland name the most contents: WA's variation sets out all of its terms, its cost and its date. Victoria's notice states the cost of the variation and its effect on the contract price, any delay estimate and whether a permit variation is needed. Queensland's document states the date of the request, the price change or how it is calculated, and when an increase is to be paid (Schedule 1B, s 41).
Victoria limits recovery on builder-initiated variations: Section 37(3) states a builder is not entitled to recover any money for its own variation unless it has complied with the section and can establish the variation was made necessary by circumstances it could not reasonably have foreseen when the contract was entered into, or the Victorian Civil and Administrative Tribunal (VCAT) is satisfied on the grounds in s 37(3)(b).
We would store the state's rule with the variation: A system-design recommendation: record which Act, which version and which contract threshold applied, and capture the fields that Act names, rather than one variation form for every state.

The variation rule, state by state

Read side by side, the five Acts answer three operational questions differently: who has to sign, whether work may start first, and what the document has to say.

In the table below, the South Australian row reports the Act's definition and s 28 as written. We did not find a provision in the Act or the Building Work Contractors Regulations 2026 that deals with variations separately, and we make no statement about how the two provisions apply to a particular variation.

State and provision	Writing and signature	Before the varied work	What the Act says it states
NSW: Home Building Act 1989, Sch 2 Pt 1 cl 1(2)	"in writing signed by or on behalf of each party"	Clause 1 sets no timing	Clause 1 sets no contents; s 7(5) requires the contract to carry a warning if the price may be varied
Vic: Domestic Building Contracts Act 1995, ss 37, 38	Builder's notice plus the owner's signed consent (builder variation) or signed request (owner variation)	Builder must not give effect to it before the signed consent or request, subject to the exceptions in ss 37(2)(b) and 38(2)	Description, reason (builder variation), effect on the work as a whole, any permit variation, delay estimate, cost and effect on the contract price
Qld: QBCC Act 1991, Sch 1B ss 40, 41	Owner agrees in writing; builder gives a written copy	No work before the owner agrees in writing; copy within 5 business days of agreement or before work starts, whichever is first	Description, date of the request, delay estimate, price change or its method, when an increase is paid or a decrease accounted for
SA: Building Work Contractors Act 1995, ss 3, 28	The Act's definition of a domestic building work contract includes "any variation of such a contract"; s 28(1) sets formal requirements for a domestic building work contract, including writing and signature	No variation-specific timing found in the Act or the 2026 Regulations	No variation-specific contents found in the Act or the 2026 Regulations
WA: Home Building Contracts Act 1991, ss 7, 8	In writing, signed by the builder and the owner or their agents	Signed copy to the owner before the work to which it relates is commenced	All of the terms, the cost, and the date of the variation

A contract threshold decides
whether the rule applies at all

None of these variation rules covers every residential job. Each sits inside a class of contract defined by price, and the five definitions use five different numbers.

South Australia's threshold moved on 10 November 2025. Regulation 4(4) prescribes the minor-work sum by the date the contract was made, so a record holding only the contract price does not show which sum the Regulations list.

State	Contracts the variation rule sits in	Threshold as published
NSW	Contracts to which s 7AA applies: those under s 7 or s 7AAA, other than contracts with a developer or a prescribed class	s 7AAA applies above $5,000 for contracts entered into on or after 1 March 2015, inclusive of GST (Home Building Regulation 2014, cl 5(2))
Victoria	Major domestic building contracts (Part 3 of the Act)	The builder will receive more than $10,000 (Domestic Building Contracts Regulations 2017, reg 6)
Queensland	Regulated contracts	Contract price more than $3,300, the regulated amount in Schedule 1B, s 1
South Australia	Domestic building work contracts other than minor domestic building work	Minor work is a cost to the building owner below $20,000 for contracts made on or after 10 November 2025, and below $12,000 for contracts made from 15 October 2001 to before that date (Regulations 2026, reg 4(4))
WA	Home building work contracts, excluding cost plus contracts	Excludes contracts of $7,500 or less and $500,000 or more (Home Building Contracts Regulations 1992, reg 2A)

Where the Acts limit a builder's own variation

The first question a builder asks is whether it can be paid for a change it initiates. The Acts answer that only in places, and in different terms.

Victoria: recovery depends on foreseeability: For a builder variation, s 37(3) states the builder is not entitled to recover any money unless it has complied with s 37 and can establish the variation is made necessary by circumstances that could not have been reasonably foreseen at the time the contract was entered into, or the Victorian Civil and Administrative Tribunal (VCAT) is satisfied there are exceptional circumstances or significant or exceptional hardship and that recovery would not be unfair to the owner. Where s 37(3) applies, s 37(4) allows the cost of the variation plus a reasonable profit.
Victoria: a 2% shortcut for owner variations: Under s 38(2), if the builder reasonably believes an owner's variation will not require a variation to any permit, will not cause any delay and will not add more than 2% to the original contract price stated in the contract, the builder may carry out the variation without the s 38(3) notice.
WA: directions and unforeseen circumstances: Section 8 lifts the s 7(1) and (2) requirements for a variation made necessary by a written direction under a written law, or by circumstances the builder could not reasonably have foreseen, if the builder gives the owner a statement of the reason and the cost within 10 working days. Section 8(4) states s 8(1)(b) does not enable a builder to vary a contract, other than under s 7(1) and (2), s 13(4) or Schedule 1, by reason only of an increase in the costs of labour or materials.
Queensland: no payment before the work: Schedule 1B, s 41(3) states that any increase in the contract price as a result of the variation can not be required to be paid before the work the subject of the variation is started.

A variation can move other obligations

A variation is not only a price change. In some states it resets dates, payment rules or insurance obligations that are recorded somewhere else.

Victoria: the contract is read as varied: Section 39 states that after a variation under s 37 or 38, references to the plans and specifications, the contract price and the completion date are read as references to them as varied or adjusted.
Victoria: a variation can trigger Home Warranty: Since 1 July 2026, s 137O(2) of the Building Act 1993 requires a builder to pay the insurance premium within 10 business days after a variation if the variation makes the contract an insurable domestic building contract, which the Act defines by the builder receiving more than $20,000.
NSW: progress payments extend to variations: A note to s 8A of the Home Building Act 1989 states that progress payments can extend to variations to the work to be done under the contract.
WA: the contract includes earlier variations: Section 7(5) states that in ss 7 and 8 a contract includes any previous variation of the contract, so each variation is made against the contract as already varied.

Why a single variation form
fails a multi-state builder.

A builder or building group working in more than one state is not filling in one kind of variation. It is filling in five, each with its own trigger, its own signatures and its own list of contents, inside a contract class whose price threshold is also different.

The practical failure is rarely a missing signature on a large change. It is the small change agreed on site, priced later, and started before anyone has the document the Act names: Queensland's written agreement before work starts, WA's signed copy in the owner's hands before the work is commenced, Victoria's signed consent attached to a notice that already stated the cost.

The second failure is threshold drift. A Victorian contract that crosses $20,000 through a variation comes within s 137O(2) of the Building Act 1993, which sets a 10 business day premium deadline. South Australia's Regulations list the minor-work threshold by the date the contract was made. Neither shows up in a variation register that stores only a description and an amount.

What we would put in a system

For each variation on a residential contract, we would test for five fields.

Where agents help here is narrow. A variation claims agent can read a site instruction, an email or a marked-up drawing, draft the variation with the fields the relevant Act names and flag a missing signature or a start date earlier than the agreement, and a person confirms it before it is sent or relied on. No agent decides whether a variation is valid, enforceable or recoverable, or whether a circumstance was reasonably foreseeable. Those are questions for the parties, the tribunal and your advisers.

Field	Why it is load-bearing
The governing Act, section and version	The rule depends on the state, and the version read (for example Authorised Version 094 in Victoria) is what a later reviewer checks against.
Who initiated it and the date of the request	Victoria treats builder and owner variations differently, and Queensland's document states the date of the request.
The signature or written agreement, with its date and signatories	The Acts name different signatories and, in Queensland and WA, tie the timing to when the varied work starts.
Cost, price effect, delay estimate and payment timing	Victoria and Queensland name these contents; Queensland bars requiring an increase to be paid before the varied work starts.
The varied work's start date, and the contract price after the variation	Start date tests the timing rule; the new price tests contract thresholds such as Victoria's $20,000 insurance trigger.

Questions worth asking
of your own variation records

For a builder working in Queensland or WA: can you show, for each variation, that the written agreement or signed copy is dated before the varied work started?

Both Acts tie the document to the start of the varied work. If the start date is not recorded, the timing rule cannot be checked after the fact.

For a Victorian builder: do your records separate builder-initiated from owner-initiated variations?

Sections 37 and 38 set different notices, different signed documents and different conditions for recovering money. A single register with no initiator field cannot show which section was followed.

For a building group: does each variation carry the state, the Act and the version you relied on?

The five Acts name different contents and signatories. Without the state and version on the record, a review has to reconstruct which rule applied to each job.

For contract administration: which contracts have crossed a price threshold through variations?

In Victoria a variation that makes the contract insurable starts a 10 business day premium clock under s 137O(2) of the Building Act 1993. The contract price after each variation is the field that answers it.

Questions people ask
about construction variations

Does a variation to a building contract have to be in writing in NSW?

Schedule 2, Part 1, clause 1(2) of the Home Building Act 1989, a term s 7E requires the contract to include, states any agreement to vary the contract, or its plans and specifications, must be in writing signed by or on behalf of each party. The clause applies to contracts to which s 7AA applies, which for contracts from 1 March 2015 starts above $5,000 inclusive of GST (Home Building Regulation 2014, cl 5(2)), as read on 9 October 2026.

What must a variation notice contain in Victoria?

For a builder variation under a major domestic building contract (the builder will receive more than $10,000), s 37(1) of the Domestic Building Contracts Act 1995 requires a notice describing the variation, why it is wanted, its effect on the work and on any permit, any delay estimate, and its cost and effect on the contract price. Authorised Version 094, as at 1 July 2026.

Can a builder start variation work before the owner signs in Queensland?

Schedule 1B, s 40(5) of the QBCC Act 1991 states the building contractor must not start any domestic building work the subject of the variation before the building owner agrees to it in writing. It applies to regulated contracts, those over $3,300, in the version current from 1 February 2026.

What are the variation rules for home building contracts in WA?

Section 7 of the Home Building Contracts Act 1991 requires a variation in writing setting out its terms, cost and date, signed by the builder and the owner or their agents, with a signed copy given to the owner before the varied work commences. The Act covers contracts above $7,500 and below $500,000, as at 5 April 2023.

What this analysis
does and does not show.

Evidence note

What it shows: How the home building Acts of NSW, Victoria, Queensland, South Australia and WA deal with variations to residential building contracts: who signs, the timing against the varied work, the contents named, the contract threshold the rule sits in, and the places where an Act limits recovery or links a variation to another obligation. As read on 9 October 2026 on each state's legislation register.
Key facts quoted: NSW Sch 2 Pt 1 cl 1(2) signed by or on behalf of each party, above $5,000 inclusive of GST; Vic ss 37 to 39, major domestic building contract above $10,000, 2% owner-variation shortcut; Vic Building Act s 137O(2) premium within 10 business days after a variation; Qld Sch 1B ss 40, 41, regulated contract above $3,300, 5 business days; SA ss 3, 28, minor work below $20,000 from 10 November 2025 and $12,000 before; WA ss 7, 8, contracts above $7,500 and below $500,000, statement within 10 working days.

We read the legislation, not the regulators' guidance pages or any tribunal decision. The NSW and SA registers were read through a rendering proxy on 9 October 2026 because the sites block automated access; the text is saved with the article.
Tasmania, the ACT and the Northern Territory are not covered. Their legislation was not read.
For South Australia we report the Act's definition and s 28 as written and did not find a separate variation provision. We do not state how they apply to any variation.
Victoria's Domestic Building Contracts Regulations 2017 were read at Authorised Version 004, as at 1 July 2021, the version the register listed as in force. We did not check for amendments not yet consolidated.
Security of payment legislation, prime cost items, provisional sums and cost escalation clauses are separate topics and are not covered.
Nothing here is legal advice, and it does not determine whether any variation is valid, enforceable or recoverable.

Bring us one month of variations.

Send us the variations from one residential job, with the dates the varied work started. We will show you which fields the governing Act names that your records hold, and which ones they do not.

This article is general information about published legislation. It is not legal advice and it does not determine whether any variation is valid, enforceable or recoverable. It covers NSW, Victoria, Queensland, South Australia and Western Australia only. All provisions are as read on 9 October 2026 at the versions listed in the sources.

Send us the variations · Variation & claims agent

Sources

Suggested citation: Home Building Act 1989 (NSW), Domestic Building Contracts Act 1995 (Vic), QBCC Act 1991 (Qld) Schedule 1B, Building Work Contractors Act 1995 (SA) and Home Building Contracts Act 1991 (WA), at the versions listed, as read 9 October 2026. Derived figures: none.

One variation, five state rules: who signs, what it states, when work can start.