"Just do it, we will sort the money later" is how tradies lose thousands. An unapproved variation is the single hardest thing to get paid for. Here is why written variations win, what the standard contracts require, and the records that make a claim stick.
Oral variations — enforceable, but a nightmare to prove
At common law a variation can be made orally or by conduct, even if the contract says "no oral variations" — but the evidentiary risk is enormous, and oral instructions are one of the biggest sources of construction disputes. The safe move: get the instruction in writing before you start, or immediately confirm an oral instruction by email, diary note and photo, then a signed variation document.
What the standard contracts require
- AS 4000: the superintendent directs variations in writing; under clause 36.2 they give written notice of a proposed variation, and you respond with the likely time and cost impact. Pricing follows the valuation hierarchy: prior agreement → applicable contract rates → schedule rates (if reasonable) → reasonable rates including profit and overheads.
- HIA / MBA residential: written variation paperwork — the owner requests the change in writing, you issue a written statement (reason, cost, time impact), and the owner signs approval before the work proceeds.
The prevention principle — your shield on delay
A party cannot claim liquidated damages for delay it caused itself — including delay from a variation it instructed. So if an owner directs a change that pushes out completion, they generally cannot hit you with LDs for that delay, provided you used the contract's extension-of-time mechanism. Use the time-claim process; do not let it lapse. More in EOT & Liquidated Damages.
The records that win a variation claim
Keep contemporaneous evidence — who asked, what changed, when, and what it cost or delayed:
- a variation register
- dated site-diary entries
- before / during / after photos
- the original instruction and any email or text confirmations
- the quote, the revised program, invoices, delivery dockets, and the signed approval.
The workflow
- Stop and identify the change immediately.
- Record it in the site diary and take photos.
- Send a written variation notice with the price and time impact.
- Get written approval before proceeding.
- Log it in the variation register and keep every source document.
Use the Variation Request / Approval form.
Common mistakes
- Doing the work on a verbal "yeah, go for it" and arguing about money later.
- Not claiming the time impact (the EOT) — only the cost.
- No variation register — so no paper trail when it is disputed.
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