Building contract red flags — the 5 clauses you should never sign
Building contracts in NZ are usually drafted by the builder or their supplier — meaning they tilt towards the builder's interests by default. Most homeowners scan them, see legal-sounding language, and sign. That's where most disputes start. This guide walks through the five specific contract clauses that should make you pause, push back, or walk away — and what to ask for instead. None of this is legal advice, but it's the practical knowledge that separates protected homeowners from exploited ones.
Red flag 1 — Cost-plus pricing without a cap
"Cost-plus" means you pay the builder's actual costs (materials, labour, subcontractors) plus a percentage margin (typically 15-25%). It sounds fair — until you realise it removes any incentive the builder has to control costs. The more they spend, the more they make. Most NZ building disasters with massive cost blowouts started with a cost-plus contract.
Cost-plus is sometimes legitimate — for genuinely unpredictable jobs like complex renovations where the scope can't be quantified upfront. But it should ALWAYS come with a cap ("not to exceed $X") or a guaranteed maximum price (GMP).
Red flag 2 — Calendar-based progress payments
Watch the payment structure carefully. "Calendar-based" means you pay on specific dates (e.g. 25% at signing, 25% on day 30, 25% on day 60, 25% on completion) regardless of work actually done. "Milestone-based" means you pay when specific physical stages are complete (e.g. foundation poured, framing up, roof on, lock-up, final).
Calendar payments allow a builder who is falling behind, or who has cash-flow issues, to keep collecting your money even when no work is being done. Milestone payments give you the leverage to withhold money until physical proof of progress exists.
Red flag 3 — Waiver of consumer rights
Some builder contracts include clauses that attempt to waive your statutory consumer rights — particularly under the Consumer Guarantees Act 1993, which entitles you to building work that's done with reasonable care and skill, fit for purpose, and completed within a reasonable time.
Look out for language like: "the customer waives all warranties, expressed or implied"; "acceptance of work is final upon payment"; "all defects must be notified within 24 hours of completion or are deemed accepted"; "the Consumer Guarantees Act does not apply".
Under NZ law, many of these clauses are not actually enforceable for residential building work — the Consumer Guarantees Act applies regardless of contract terms in most domestic contexts. But the presence of these clauses tells you something about the builder's mindset: they're already planning for disputes and trying to make recovery harder for you.
Red flag 4 — Excessive deposit (>10%)
Most reputable NZ builders ask for 5-10% deposit at contract signing, with the balance paid against milestone progress. A deposit demand above 10% is the single strongest signal of cash-flow trouble.
Builders ask for large deposits because they need your money to pay outstanding debts to other suppliers or fund their next job. If they're asking for 20-30% upfront, they likely can't fund your job's startup costs themselves — meaning your money is funding their cash gap, not your materials.
There are some legitimate exceptions — very large bespoke joinery orders, prefabricated structural elements, custom imported materials. But these should be itemised and accompanied by proof of supplier orders.
Red flag 5 — No defect-period or completion guarantee
Reputable builders offer a defects-liability period after completion — typically 12 months — during which they'll come back to fix any issues that arise from their workmanship at no cost. Some go further with structural guarantees of 10 years (Master Build Guarantee, Halo).
If the contract is silent on the defects period, or attempts to limit it to 30 days, that's a flag — the builder is signalling they don't expect to be around to honour longer warranties.
If no third-party completion guarantee is offered (Master Build, Halo, or similar), you have no protection if the builder fails before finishing your job. For large projects, the cost of a third-party guarantee ($200-$500) is trivial compared to the protection.
What a good contract actually looks like
A homeowner-friendly NZ building contract has: a fixed-price total with a clear scope of work, milestone-based payments tied to physical completion stages, explicit acknowledgement of Consumer Guarantees Act / Fair Trading Act protections, a deposit of 10% or less, a 12-month minimum defects-liability period, and either a Master Build or Halo guarantee for projects above $50k.
Master Builders (masterbuilder.org.nz) and NZ Certified Builders (nzcb.nz) both publish standard residential building contract templates that include these protections. If your builder won't use one of these templates, that itself is a flag.
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Frequently asked questions
- Should I get a lawyer to review my building contract?
- For renovations over ~$100k or new builds, yes — a 1-hour consult ($300-$500) can save you tens of thousands. For smaller jobs, the cost may not be justified, but at minimum compare what you've been offered against the Master Builders or NZCB standard residential templates.
- Can I add my own clauses to the contract?
- Yes — building contracts are negotiable. Any clause you add or amend needs to be initialled by both parties. Common additions: limits on cost variations, requirement to use NZ-made materials, retention amounts (where you hold 5-10% back for 90 days after completion to ensure defects are fixed).
- What's a 'retention' and should I include one?
- A retention is an amount (typically 5-10% of the contract value) held back at completion and released after a defects-liability period (usually 90 days). It gives you leverage to ensure defects are fixed. Most large commercial contracts include retentions; smaller residential contracts often don't, but you can negotiate to add one.
- What if the builder refuses to change any clauses?
- That itself is information. A builder who won't negotiate any terms is signalling rigidity — and probably resistance to accountability when things go wrong. Reputable builders expect customers to want changes and are flexible. Walk away from one who won't budge at all.
- Should I sign anything on the day they quote?
- Never. Take the contract home, read it carefully, get a second opinion if it's a large job, and sleep on it. High-pressure "sign today or the price goes up" tactics are themselves a red flag.
Related guides
This guide is general information for NZ homeowners and is not legal or financial advice. Names of registers, associations and dispute bodies are accurate at time of publication. Always confirm critical details on the official source before acting.