Guide · Variations
The variation clause: what your contract should say
Most tradies read the price page of a contract and skim the rest. But on any job where the scope moves — which is most jobs — the variation clause decides who pays for the changes. Here's what a workable one covers, and why the clause alone won't save you.
Last updated 2026-07-11 · Reviewed by the TradieCue team
A workable variation clause in a building contract should require that (1) all variations be put in writing, (2) extras be priced by a stated method (agreed lump sum, schedule of rates, or cost plus a stated margin), (3) varied work be approved before it starts, and (4) variations that add work also extend the completion date. Just as important: your on-site practice has to match it — a clause requiring written variations works against you if yours never are.
Why the variation clause matters more than the price page
The contract price only tells you what the job pays if nothing changes. On building work, something always changes: the customer upgrades a finish, the wall comes off and the frame is rotten, the certifier wants something the plans didn't show. Each of those moments is money — yours or the customer's — and the variation clause says whose. A tight price page with a vague variation clause is a fixed fee for an unfixed job.
What a workable clause covers
Variations must be in writing. The clause should say scope changes are documented and accepted in writing before they form part of the contract. That protects both sides: the customer can't claim the extra was always included, and you can't be accused of inventing work afterwards.
How extras are priced. The weakest common wording is "variations to be agreed" — which prices nothing and guarantees a negotiation at the worst possible moment. Better: a lump sum quoted per variation before the work; a schedule of rates (hourly labour rates, materials at cost plus a stated percentage) for when a lump sum isn't practical; or cost-plus with a stated margin. Whichever method, it goes in writing before the job starts, not mid-argument.
Approval before the varied work starts. The clause should require the customer's written go-ahead before the extra work happens, with a carve-out for urgent or safety-related work (proceed, then document immediately). This is where your bargaining power lives: a customer deciding whether to pay for work not yet done is a negotiation; a customer deciding whether to pay for work already done is a dispute.
Time as well as money. Extra work takes extra days. If the clause is silent on time, every variation quietly compresses your schedule — and if the contract has a completion date with consequences, you're funding the overrun. Each variation should state its effect on the completion date, even when that effect is nil.
This is general information, not legal advice. Contract law and domestic building rules differ by state, contract type and job value, and the exact wording of a variation clause matters enormously. Don't copy clause language from a web page — this one included. Have a construction lawyer draft or review your terms, or start from a standard-form contract, and check your state building authority's requirements for residential work. We're deliberately not quoting statutory text: it changes, and context decides how it applies to you.
The clause is only half the system
Here's what undoes tradies with perfectly good contracts: a variation clause describes a practice. If the contract says variations will be written and approved, and your actual habit is "yeah, no worries" and a mental note, the clause doesn't just fail to help — it can hurt. You're the one who agreed changes would be documented, and at dispute time the customer gets to ask why none of yours were. The fix isn't legal, it's operational: make writing the variation as easy as saying yes to it.
Working under the client's contract
Subbies and small builders often work under someone else's terms — a head contractor's subcontract or a customer-supplied agreement. Before signing, read the variation clause for three things: notice periods (some contracts bar payment for extras unless written notice lands within a set number of days — miss the window, lose the money), whose form counts (if variations are only valid on the builder's paperwork, submit through their process and keep your copy), and who has authority (a supervisor's verbal go-ahead may bind nobody). You can't change their clause, but you can run your paperwork to satisfy it.
Standard-form contracts vs handshake jobs
For bigger residential work, standard-form contracts from state master builder associations and HIA-style bodies come with variation clauses drafted by lawyers and tested in real disputes — a far safer starting point than words you assembled yourself. At the other end, plenty of trade work runs on a quote and a handshake. There, your quote's terms are your variation clause: even two sentences — extras agreed in writing before the work, priced at the rates in this quote — put you miles ahead of pure verbal agreement.
A worked example
Mid-bathroom-reno, the owner asks for a second towel rail and a niche in the shower wall. The contract's variation clause requires written variations, priced and approved before the work, with any time impact stated.
Variation No. 2 — 8 Warrick St bathroom (Contract dated 4 May)
The clause set the rules; this document is the clause being followed. Either half without the other is where disputes start.
Common mistakes
- "Variations to be agreed." Not a pricing method — a deferred argument. Name the method: lump sum, rates, or cost plus a stated margin.
- A clause your habits contradict. If the contract requires written variations, undocumented extras are you breaching your own terms.
- Signing the client's contract without reading its notice periods. Some subcontracts kill your right to payment for extras if written notice is late.
- No time provision. Ten approved variations and an unchanged completion date means you donated the schedule.
- Copying clause wording off the internet. Including from here. Standard-form contracts and construction lawyers exist for exactly this.
Where TradieCue fits
TradieCue doesn't write your contract — a lawyer or a standard-form document does that. What it fixes is the half contracts can't reach: producing the written variation on site, the moment the change is agreed. Say it out loud — "Warrick St, they want a niche in the shower wall and a second towel rail, $700 plus GST, adds a day" — and Timmy drafts a variation on the right job with your figures. Prices come from the user and stay editable. Timmy structures the work and wording; it does not invent amounts. Nothing is sent automatically. Every quote, variation and follow-up is a draft the user reviews, edits and shares themselves. And like any generated document, the draft is paperwork help, not legal advice.
For what goes inside the document, see what to include in a building variation; for the day-to-day habits, how to document extra work.
Common questions
Do I need a variation clause on small jobs?
You need the practice more than the clause. On quote-and-handshake work, two sentences of terms on the quote — extras agreed in writing before the work, priced at stated rates — plus an actual written note per change gives you most of the protection. The bigger the job, the more the formal clause matters.
What if the customer's contract has a variation clause I don't like?
Raise it before signing — notice periods and pricing methods are routinely negotiated. If you sign as-is, run your paperwork to satisfy their clause: use their forms, hit their notice windows, and get approval from someone with authority under that contract.
Is a verbal variation ever enforceable?
Sometimes, depending on the contract, the state and the evidence — but 'sometimes, with a fight' is the point. For registered domestic building work, several states restrict recovering payment for undocumented variations. Ask a construction lawyer about your situation; writing it down at the time is cheaper than finding out.
Where do I get a properly drafted variation clause?
A construction lawyer, or a standard-form contract from your state's master builder association or an HIA-style body. Your state building authority also publishes guidance on what residential contracts must contain. Avoid assembling wording from web pages — including this one.
Try it on your next job
TradieCue is free to download on the App Store. Say a rough note about a real job and review the draft Timmy produces — nothing is sent until you share it yourself.
Free to download and try. TradieCue Pro is a subscription through Apple: A$24.99/month or A$239.99/year with a 30-day free trial. Apple confirms before any charge.