Variations on a Pool Contract: The Two Timing Rules

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A variation is any change to the materials or work under your pool contract — rock in the excavation, extra piering, a change of coping. In Queensland it must be agreed in writing before the work commences, and the increase cannot be required to be paid until that work starts. On contracts of $20,000 or more, the price sits on page 1.

The short answer

Agreement comes before the work, not after. All variations must be agreed in writing by the home owner before the variation work commences.
Payment cannot be demanded before the work starts. Any price increase due to a variation cannot be required to be paid until the variation work is started.
The QBCC names variations as a frequent cause of cost overruns and building disputes — the regulator's own words, in the guide every Queensland owner is given.
Every variation that adds work can move your finish date. Approving a variation involving extra work is a recognised ground for an extension of time.
A verbal “we'll sort it out later” is the failure mode. By the time it is written up, both of your checks have already expired.

The two timing rules, and what each one protects
	Rule 1 — agreement	Rule 2 — payment
What the rule says	All variations must be agreed in writing by the home owner before the variation work commences	Any price increase due to the variation cannot be required to be paid until the variation work is started
What it protects you from	Being presented with a change you never approved	Paying for a change that has not begun
When you lose it	The moment work starts without written agreement	The moment you pay on request rather than on commencement
The signal to watch for	“We'll write it up later”	An invoice for a variation you cannot see any work on
What to do instead	Ask for the scope and price in writing, then decide	Pay when the work has started, as the rule allows
Knock-on effect	An approved variation adding work is a ground for an extension of time	The contract price on page 1 of the schedule changes

What counts as a variation, and why pools produce so many

The definition is broad. The QBCC's consumer building guide states: “Any change to the materials used or work to be performed under the contract is known as a ‘variation’.” It then adds, in the regulator's own words, that “variations are frequently the cause of cost overruns and building disputes.”

Pool builds generate variations at an unusual rate, and the reason is structural rather than cultural. A pool contract is signed before anyone has seen what is under the ground. The things most likely to change are the things nobody could price accurately at signing:

Rock or unexpected ground conditions found during excavation — the classic pool variation, and often the largest.
Access proving tighter than assumed, turning a machine dig into a crane job or a hand dig.
Engineering changes after a soil report, such as additional piering or a thicker shell.
Owner-driven upgrades — a change of coping, tile, lighting or heating once the shape is visible on site.

The first three are genuine and mostly unavoidable. That is exactly why the timing rules matter: a variation being legitimate is a separate question from whether it was handled properly. Our guide to provisional sums in a pool quote covers the related mechanism where a cost was anticipated but not fixed.

Rule one: agreement before the work commences

The guide states that “all variations must be agreed in writing by the home owner before the variation work commences”.

Three words carry the rule. Written — not a conversation on site. By the home owner — not noted by the builder. Before the work commences — not before the invoice.

The practical effect is that you are entitled to know the scope and the price of a change while you still have the option of saying no. Once the rock is out and carted away, your negotiating position is a discussion about a cost already incurred. Before it comes out, it is a decision.

The realistic script, when a builder rings from site to say they have hit rock: agree that the work needs doing, and ask for the variation in writing with the scope and the price before the machine starts. On a genuine variation this is a short delay and no builder will object to it. Where it is resisted, the resistance is itself the information.

If a variation has already been done without agreement, you are not without options, but you are in a different conversation — see why a pool costs more than the contract, which deals with the after-the-fact case.

Rule two: payment cannot be required until the work starts

The second rule is less known and does real work: “any price increase due to the variation can not be required to be paid until the variation work is started.”

This sits alongside the general progress-payment principle in the same guide, that a claim must be “directly related to work progress on site and proportionate to (or less than) the value of the work that relates to the claim” — illustrated there with the line “you should not pay 50% until at least half of the work is completed on site”.

Together the two rules bracket a variation at both ends. You approve before it begins; you pay once it has begun. An invoice arriving between those two points — approved but not started — is early, and saying so is not a dispute, it is the rule.

This matters most on the variations that are ordered long before they are performed: an upgraded heater, a change of tile, additional paving. Those can be agreed in month one and installed in month four. The money is not payable at agreement. It is payable at commencement.

Deposit and progress payment limits apply separately and are worth knowing alongside this — see pool deposit limits and progress payments.

The part almost nobody connects: variations move your finish date

A variation changes two numbers, and most owners only watch one.

The QBCC guide sets out the grounds on which a contractor may seek to extend the Date for Practical Completion, and names among them the case where you “approve a variation to the contract which involves extra work”. It sits in the same list as owner-caused delay and unusually wet weather.

So every variation that adds work is also a legitimate claim on your calendar. Approving four modest upgrades across a build is approving four extensions of time, each individually reasonable. That is how a pool contracted for summer is finished in autumn without anybody doing anything wrong.

The mechanism is worth stating precisely, because it protects you in both directions:

An extension must be claimed in writing, and you “should carefully consider (not unreasonably reject) and respond to promptly in writing”.
If you approve it, the Date for Practical Completion is extended by the period claimed.
If you do not, the extension is deemed ‘disputed’ — it does not simply vanish.

The useful habit is to ask one extra question every time a variation is put in front of you: how many days does this add? Get the answer in the same document as the price. A variation priced in dollars alone is only half quoted, and the missing half is the one that decides whether the pool is ready for the season you bought it for. If the build has already slipped past its date, working out the real due date starts with the commencement notice and every approved extension since.

And if you are not yet under contract, how a builder handles rock and ground conditions is one of the most useful things to compare side by side while gathering pool quotes — the variation clause is where that difference shows up in writing.

Common questions

Does a pool variation have to be in writing?

Yes. The QBCC's consumer building guide states that “all variations must be agreed in writing by the home owner before the variation work commences”. Written agreement by the owner, before the work starts — a verbal agreement on site followed by paperwork afterwards does not meet the rule.

Can my builder make me pay for a variation before the work is done?

No. Any price increase due to a variation cannot be required to be paid until the variation work is started. That applies even where you agreed to the variation weeks earlier, which is common for upgrades ordered early and installed late.

What if the builder does variation work without asking me?

The requirement is agreement in writing before the work commences, so work carried out without that has not followed the rule. Raise it in writing straight away, ask for the scope and price that should have been provided beforehand, and keep the correspondence. Where a dispute develops, the QBCC offers a free Early Dispute Resolution service.

Do variations change my completion date?

They can. Approving a variation that involves extra work is one of the recognised circumstances in which a contractor may seek to extend the Date for Practical Completion. The claim must be made in writing and you should respond promptly in writing; if you do not approve it, the extension is treated as disputed rather than simply refused.

Is a variation the same as a provisional sum?

No. A provisional sum is an allowance written into the contract for work whose cost could not be fixed at signing, and it is adjusted when the real cost is known. A variation is a change to the materials or work itself. A build can produce both, and they are documented differently.

Sources

General information only, current at 2026-09-20. Pool rules differ by state and by council, and penalty amounts are updated regularly. Confirm your own obligations with your council or a registered inspector before acting.

What is a variation on a pool contract?