The variation is where most builder disputes are won and lost. The customer signs a contract for $280,000. By practical completion the bill has reached $326,000. The builder produces a stack of variation forms. The customer can’t quite remember signing all of them and isn’t sure whether the maths is right. Some of the items look reasonable. Some don’t. Working out which variations actually bind you, and which don’t, is one of the most useful skills a residential customer can develop. Most variations dispute battles boil down to whether the paperwork was done properly at the time.
Here’s how to read a builder’s variation properly under Australian residential building law, what makes one binding, and what to do when the variation paperwork doesn’t add up.
What a variation actually is
A variation is any change to the original contracted scope of work, the materials, or the price. It can be requested by the customer (a different tap, an upgraded floor, an additional power point) or by the builder (an unforeseen condition that needs different work, a substitution because the originally specified product is no longer available). Either way, the variation needs to be documented, priced and approved before the work happens. The original contract sits underneath, and the variations sit on top, adjusting price and scope as the job evolves.
Most state laws require variations to be in writing
Residential building legislation in NSW (Home Building Act), Victoria (Domestic Building Contracts Act), Queensland (Domestic Building Contracts Act) and equivalent acts elsewhere all require variations to be documented in writing, signed by both parties, and to include a description of the change, the impact on price, and the impact on the contract date. A verbal variation, even one the customer agreed to, is generally unenforceable in residential building above the legislative threshold. The builder who didn’t write it down may not be entitled to recover for it.
A signed variation is a small contract
Read each variation as if it were a small contract. Description: what is being changed. Price: the dollar impact, including whether it adds or subtracts from the contract sum. Time: how the change affects the completion date. Date and signature from both sides. Cross-reference: which clause or section of the original contract is being amended. A variation that doesn’t include all of these is at best loose, at worst unenforceable. The standard residential contracts in each state include variation forms with these fields built in for a reason.
Customers can refuse variations
A customer is generally not obliged to accept a variation just because the builder has proposed one. If the change is being driven by something the customer wants, the price has to make sense before they sign. If the change is being driven by something the builder is now claiming was unforeseen, the customer is entitled to ask whether the issue should have been allowed for in the original quote, and whether the builder is genuinely entitled to recover the extra cost or whether it falls within their original scope and risk.
Spot variations that should have been in the original quote
One of the most common variation tactics is to invoice as a variation things that should have been in the original quote. The bracing the building approval clearly required. The waterproofing layer specified in the plans. The hardware needed to comply with the National Construction Code. Each of these was foreseeable from the documents on the day the contract was signed. A builder who variations them later is, in effect, being paid twice. Customers reading variations should ask whether the item was in the original drawings, the engineering, or the regulatory minimums.
Allowances and provisional sums adjust differently
Allowances and provisional sums in the original contract are not variations. They are placeholders. When the actual cost lands, the contract sum is adjusted up or down by the difference. That adjustment isn’t a variation, even if some builders document it as one. Customers should keep the two concepts separate: an allowance landing $400 over its budgeted figure is an adjustment, not a $400 variation requiring a fresh sign-off. The total still moves, but the legal mechanism is different and the paperwork is different.
Don’t sign variations under pressure on site
Builders sometimes present variations on site with the work already underway, asking the customer to sign quickly so the day isn’t lost. Don’t. Even a small variation should be read carefully before signing. Take the form home. Compare it to the contract and the plans. Check the numbers. If the work has already been done, the dynamic shifts: the builder may try to argue the customer authorised verbally and accepted the work, but a fairly worded post-fact variation is still better than no document at all. The customer who pushes back on rushed variations almost always ends up with cleaner paperwork.
Cross-check the running contract sum
Each variation should change a clearly identifiable running figure. After three signed variations, the contract sum should be the original price plus or minus the sum of those variations. Many disputes arise because the running total isn’t tracked properly, with variations sometimes counted twice, items duplicated, or errors compounding silently. Keep a simple spreadsheet: original sum, variation by variation, current contract sum after each. The figures should match the builder’s progress claims and the final invoice.
When a variation isn’t valid
If a variation wasn’t in writing, wasn’t signed, didn’t describe the change, didn’t price the change, or was outside the customer’s authority, it may not be enforceable under the relevant state’s act. The customer is generally entitled to dispute the variation, decline to pay it, or pay it under protest pending resolution. The builder’s recovery rights are weaker when the variation paperwork wasn’t done properly. State regulators and tribunals routinely uphold customers who held the line on variation requirements.
A builder’s variation is a small but important piece of contract paperwork. Read each one carefully: description, price, time, signature, cross-reference. Refuse to sign on the spot. Keep a running total. Question variations for items that should have been in the original scope. Dispute variations that don’t meet the legal requirements. The customers who treat variation paperwork seriously almost always pay closer to the original contract sum. The ones who don’t usually overpay by a quiet margin nobody spelled out.