Renovation Over Budget? The Variation Check to Run Before You Pay the Final Invoice (NZ)

sp8002
May 31
4 min read

Renovations overrun more than new builds because hidden conditions surface mid-job and become variations. Before you pay a renovation final invoice, run this check — the "found conditions" line is where most over-charging hides.

By Steve Parker · Trueworks · NZ construction contract review · 6 min

What you'll learn

Why renovations overrun more than new builds
Legitimate "found conditions" versus over-reach
A final-invoice check built for renovations

Quick answer: Renovations overrun more than new builds because hidden conditions — rot, old wiring, failing foundations — surface mid-job and become variations. Before you pay a renovation final invoice, run a check: confirm each extra is a genuine variation rather than the builder's under-pricing; that each was notified in writing before the work; that provisional-sum and PC-sum adjustments carry only the agreed margin; and that the breakdowns are substantiated. On a renovation, the "found conditions" line is where most over-charging hides.

A renovation is a build on top of an unknown. Once the linings come off and the floor comes up, the job meets whatever the previous decades left behind — and that is the legitimate engine of renovation variations. It is also the cover under which an over-priced final account can travel. The two look similar on an invoice. This check separates them.

Why renovations overrun

New builds start from a clean, fully-specified design. Renovations start from a guess about what is behind the wall. When the guess is wrong — borer in the bearers, a sub-standard switchboard, a foundation that will not take the new load — the fix is real, necessary, and usually a genuine variation. Expect some of this on any renovation. The question is never "should there be variations" but "is each one genuine, notified, and fairly priced."

"Found conditions" — legitimate versus over-reach

A legitimate found-condition variation has three marks: it was genuinely not visible or knowable at pricing; it was raised with you in writing when discovered, before the work; and it is priced with a breakdown. Over-reach shows the opposite signs — conditions a competent builder should have allowed for, raised only on the final invoice, or priced as a round number with no working. The distinction is the heart of most renovation disputes.

The renovation final-invoice check

List every extra on the final account against the original contract scope.
Classify each — genuine variation, provisional-sum adjustment, PC-sum adjustment, or fluctuation. (See provisional sums vs variations.)
Check the timing — was each variation notified in writing before the work, per the 10-working-day rule, or did it appear for the first time on the final invoice?
Check the breakdowns — labour, materials, and a single agreed margin, substantiated.

Check the provisional sums — on renovations these are often large (drainage, re-piling, re-wiring) and adjusted to actual cost; confirm the actual cost is substantiated and the margin is not doubled.
Check for the builder's own under-pricing — anything that is really "we underestimated the original scope" is generally the builder's risk on a fixed price, not a variation.

What to do before you pay

Pay the undisputed lines. Put the questioned lines to the builder in writing, with the classification and the clause, and ask for the missing substantiation. If the contested figure is large, a written, clause-cited read of the final account turns a vague "this feels too high" into a specific, defensible position. If it does not resolve, see how to dispute a building variation.

Send Trueworks your contract and the line in question. You receive a written, code-cited assessment of whether it was identified, notified, and priced the way the Building Act and your contract require — a second opinion you can put straight in front of your builder. NDA available; files NZ-hosted. → Email steve@trueworks.co.nz
or start at trueworks.co.nz

Not sure a variation or charge on your build is justified?

FAQ — Renovation overruns in NZ

Are renovation variations normal? Yes. Hidden conditions make some variations almost inevitable on a renovation. What matters is whether each is genuine, was notified in writing before the work, and is fairly priced.

The builder found rot and charged a variation — do I pay? If it was genuinely not knowable at pricing, was raised with you before the work, and is substantiated, it is a legitimate variation. If it was foreseeable, late, or unsubstantiated, question it.

Can a builder blame the overrun on "the age of the house"? Some of it, legitimately. But age does not excuse foreseeable items, missing notice, or unsubstantiated pricing. Each line still has to stand on its own.

Should provisional sums be large on a renovation? Often, yes — for groundworks, drainage, and re-piling that cannot be scoped until work starts. Confirm each is adjusted to a substantiated actual cost with a single margin.

When is it worth getting a review? When the contested portion of a renovation final account runs into four or five figures, a written clause-cited read is usually worth far more than its cost.

How Trueworks helps

Trueworks reads a renovation final account line by line against the original scope and your contract — separating genuine found-condition variations from foreseeable items, late notices, and doubled margins. You get a written, code-cited account of what stands and what is open to question, before you pay.

About Trueworks

Trueworks is built by Steve Parker — 20 years on the analytical side of NZ construction: variation reviews, contract advisory, and AI-augmented document analysis. It is the same defensible, code-cited read a quantity surveyor would give a variation, made available to the homeowners and trades on the receiving end of one. I answer every email personally during pilot phase.

steve@trueworks.co.nz · trueworks.co.nz