Implied Warranties in the Building Act 2004 — Your Rights When Building Work Is Defective (NZ)

Steve Parker

Jun 15

9 min read

Updated: Jul 26

If residential building work in New Zealand is defective, the Building Act 2004 implies a set of warranties into your contract --- covering competent workmanship, compliance with the plans and the Building Code, and fitness for occupation. These warranties cannot be contracted out of, and for the first twelve months after completion the onus sits with the builder to show the work complied.

By Steve Parker · Trueworks · NZ construction document analysis · 6 min

Most homeowner disputes we are asked to look at are not about price. They are about quality --- a deck that ponds, a shower that leaks at the upstand, cladding junctions that were never sealed, a floor that was not level. The owner suspects the work is defective, the builder says it is within tolerance, and nobody has written down what the contract and the Building Code actually required. This post sets out the statutory warranties that apply to that situation, and the practical step that decides most of these disputes: documenting whether the work met the specified standard.

The implied warranties --- Building Act 2004, section 362I

For residential building work, section 362I of the Building Act 2004 implies a set of warranties into every contract, whether or not the contract is in writing. In summary, the builder warrants that:

the work will be carried out in a proper and competent manner, and in accordance with the plans and specifications in the contract;
all materials used will be suitable for the purpose for which they are used, and --- unless the contract states otherwise --- will be new;
the work will comply with the Building Act, the Building Code and all other applicable enactments;
the work will be carried out with reasonable care and skill, and completed by the date (or within the period) specified, or otherwise within a reasonable time;
the household unit, if the work involves one, will be suitable for occupation on completion; and
where the owner has made known the particular purpose for which the work is required, the work and any materials will be reasonably fit for that purpose, and of a nature and quality reasonably expected to achieve that result.

These are not optional extras a builder grants you. They are read into the contract by statute.

They cannot be contracted out of --- section 362K

Section 362K makes the warranties mandatory. A provision in a building contract that tries to exclude, restrict or modify the implied warranties has no effect to the extent that it does so. A clause saying "no warranty is given beyond defects notified in writing within 30 days" does not displace the section 362I warranties. This matters because owners often assume that whatever the contract says is the whole of their rights --- it is not.

They run with the building --- section 362J

The warranties are enforceable not only by the person who contracted for the work but by subsequent owners of the household unit. If you buy a home and a latent defect in recent building work surfaces, you may have a claim against the original builder even though you never signed the contract. The warranty attaches to the work, not only to the original parties.

The twelve-month onus --- section 362Q

Section 362Q is the provision homeowners most often do not know about. If, within twelve months after the building work is completed, the owner notifies the builder of a defect, and the defect is one that would be a breach of an implied warranty, the work is presumed to be in breach unless the builder proves otherwise. Inside that twelve-month window the onus is reversed: the builder has to demonstrate the work complied, rather than the owner having to prove it did not.

That reversal is powerful, but it has a precondition --- you have to notify the defect, in writing, within the twelve months. A defect raised on day 360 in an email that describes the problem and asks for it to be remedied preserves the position. The same defect raised informally over the phone, with nothing in writing, often does not.

Workmanship warranty NZ --- what "proper and competent" actually means in practice

The Act does not define "proper and competent manner", and this is where most defective-workmanship arguments actually play out. In practice the benchmark is built from two layers: the contract documents first, then the Building Code. If the drawings, the specification or a named manufacturer's installation instructions set a standard, that is the standard the work is measured against. Where the contract is silent, the Building Code sets the floor --- work that fails a code clause fails the warranty regardless of what the builder considers acceptable practice. "Proper and competent" is assessed against those documents, not against what the builder usually does or what a mate says looks fine.

Tolerance arguments sit on top of that. MBIE publishes guidance on tolerances, materials and workmanship in new residential construction, which sets out commonly accepted tolerances for things like level, plumb, alignment and surface finish --- and it is what a builder is usually reaching for when they say the work is "within tolerance". Two things matter about that guidance. First, it is guidance, not law: it describes what a competent builder would normally achieve, and a tribunal or adjudicator will treat it as a reference point where the contract says nothing. Second, it does not override the contract --- if the specification calls for a higher standard than the guidance tolerance, the specification governs. A builder cannot quote a generic tolerance to excuse work that fails the standard the parties actually agreed.

Which is why written documentation of the specified standard decides most of these disputes. When an owner can put the contract drawing, the code clause or the manufacturer's specification next to a measured deviation, the tolerance argument usually collapses --- the question stops being whose opinion of good workmanship prevails and becomes whether the work matches the documented requirement. When neither side can produce the specified standard in writing, the dispute degrades into opinion against opinion, and the party with the better records generally wins. Before arguing about whether workmanship is acceptable, establish in writing what standard it was required to meet.

After twelve months --- the ten-year longstop

The twelve-month onus reversal ends, but the warranties themselves do not. Claims for defective building work remain available, subject to the Building Act's longstop in section 393: no proceeding relating to building work may be brought more than ten years after the act or omission on which it is based. After the first year the owner carries the onus of proving the breach --- which again turns the dispute into a question of evidence.

The disclosure regime --- the Building (Residential Consumer Rights and Remedies) Regulations 2014

For residential building work above the prescribed threshold of $30,000 (including GST), the builder must, before the contract is signed, give the owner a prescribed checklist and a disclosure statement, and must provide a written contract. After completion the builder must provide an owner's maintenance and insurance information pack. Failure to comply carries an offence and a penalty. If your project was over that threshold and you never received the checklist, the contract or the post-completion pack, that itself is a compliance failure worth recording. We cover the written-contract requirement in more detail in our note on the $30,000 written contract rule.

The Consumer Guarantees Act overlaps

The Consumer Guarantees Act 1993 also applies where you engage a builder as a consumer. It guarantees that services are carried out with reasonable care and skill, are fit for any particular purpose made known, and are completed within a reasonable time. For residential building work the two regimes run in parallel --- the Building Act warranties are construction-specific and cannot be contracted out of, while the Consumer Guarantees Act adds a second statutory layer. You do not have to choose one; the relevant point is that your rights are broader than the contract alone.

Where these disputes are actually won

Notice what every one of those sections has in common. The warranty sets a standard --- proper and competent work, compliance with the plans, compliance with the Building Code, fitness for purpose. Whether the work in front of you met that standard is a technical question, not a legal one. The Disputes Tribunal, an adjudicator or a court does not start by reading the Act; it starts by asking what the drawings and the Building Code required, and what was actually built.

That is the gap most homeowners fall into. They know something is wrong, but they cannot state --- in writing, against a cited clause --- exactly which requirement the work failed. "The deck leaks" is a complaint. "The membrane upstand is 90 mm where E2/AS1 requires a minimum 150 mm at the door threshold, and the as-built does not match consented detail 7" is evidence. The first invites an argument; the second invites a remedy.

How to document a defect claim

If you suspect residential building work is defective, the practical sequence is:

Notify in writing, inside twelve months. A dated email describing each defect and asking the builder to remedy it preserves the section 362Q onus reversal.
Gather the documents. The signed contract, the consented drawings and specifications, the producer statements, and photographs of the work as built.
Identify the specified requirement for each defect. What did the contract drawing, the manufacturer's specification or the relevant Building Code clause require?
Compare it to what was built. This comparison --- requirement versus as-built --- is the substance of the claim.
Keep the standard cited and neutral. A defect record that names the clause and states the deviation is far harder to argue with than an emotive complaint.

Steps 3 and 4 are where an independent technical review earns its place. A code-cited assessment of whether the work matches the contract documents and the Building Code gives you the evidence layer the statutory remedies depend on --- the same analysis we apply when an owner asks whether a charge is justified. If you are weighing up a defect or a disputed final invoice, our independent building variation and quote review sets out what an assessment covers.

What an independent review can and cannot do

To be clear about scope: a technical document review establishes whether the work, as built, departs from the plans, specifications and Building Code, and records that against the cited standard. It is analysis, not legal advice, and it is not a Building Act determination from MBIE or a Disputes Tribunal ruling. It is the evidence those processes rely on. If your dispute needs a binding decision, the routes are set out in our note on the Disputes Tribunal, adjudication and court, and where the disagreement is about a variation rather than a defect, see how to dispute a building variation and the difference between a variation and a builder fixing their own mistake.

FAQ --- implied warranties and defective work

Is there a 10-year warranty under the Building Act?

Not as such. The ten-year period people refer to is the longstop in section 393 of the Building Act 2004, and it is a limitation period, not a warranty --- it limits when a claim can be brought, barring civil proceedings relating to building work more than ten years after the act or omission they are based on. The implied warranties themselves have no fixed expiry inside that window; what changes after the first twelve months is only the onus of proof, which shifts from the builder back to the owner.

Can a builder contract out of the implied warranties?

No. Section 362K provides that a provision purporting to exclude, restrict or negate the section 362I warranties has no effect. A contract clause limiting defect claims to a shorter notification period, or disclaiming the warranties altogether, does not displace them --- the statutory warranties apply regardless of what the contract says.

Get a defect or variation reviewed

Send us the contract, the consented drawings and photographs of the work in question. We return a code-cited assessment of whether the work meets the specified standard --- the evidence layer your statutory remedies rely on. No charge for your first review packet. NDA available; files NZ-hosted and deleted after 30 days unless you ask us to retain them.

→ Get the free check at trueworks.co.nz/contact --- or email hello@trueworks.co.nz

About Trueworks

Trueworks is built by Steve Parker --- 20 years on the analytical side of NZ construction. Independent, citation-backed second opinions on construction documents for homeowners, builders and trade subcontractors: variation reviews, quote checks and defect assessments against the contract, the relevant NZ standards and the Building Code. Analysis, not legal advice. I answer every enquiry personally.

hello@trueworks.co.nz · trueworks.co.nz

Sitting on a variation, claim or contract clause you are not sure about? Send it with the contract --- a written, code-cited answer back within 24 hours. Send us the drawings and the quote, tender or variation. You get a written, code-cited check back within 24 hours. No charge for your first check. No card, no obligation. NDA available.→ Get the free check at trueworks.co.nz/contact --- or email hello@trueworks.co.nz