Are Contractors Liable for Defective Building Materials in New Zealand?

In New Zealand, contractors who supply and install materials for residential building work may still be liable if those materials fail, even if they did not manufacture or design them. Under the Building Act 2004 and the Consumer Guarantees Act 1993, contractors can be responsible for ensuring supplied materials are fit for purpose, durable, and suitable for their intended use. That liability can arise years after the work is completed.

Why can contractors be liable for supplied materials?

You finish a job, get paid, and move on.

Five years later the phone rings.

A light fitting has failed. A plumbing fitting is leaking. A cladding product hasn’t lasted. The client wants it fixed, and they want you to pay for access, removal, replacement, and reinstatement.

You didn’t manufacture the product. You didn’t design it. You installed what was specified or supplied.

Yet under New Zealand law, you may still be liable.

For builders, electricians, plumbers, HVAC installers, and other trades, two pieces of legislation quietly create long-term and often underestimated risk:

  • The Building Act 2004 (“Building Act”), and
  • The Consumer Guarantees Act 1993 (“CGA”).

Understanding how these laws work, and how they interact, is essential for every contractor supplying and installing materials. This article focuses only on the obligations that relate to supplying materials to residential consumers.

What implied warranties apply under New Zealand law?

For residential building work, the Building Act and CGA automatically implies warranties into every contract, whether written or verbal. These warranties cannot be excluded or reduced.

The Building Act implies that you warrant that building products used will be suitable and fit for purpose.

The CGA follows a similar vein, in implying that you warrant that the goods you supply to a consumer will generally:

  • Be of acceptable quality;
  • Be reasonably fit for their purpose;
  • Be free of defects;
  • Match descriptions and representations; and
  • Be durable.

In a nutshell, if you supply and install materials, you are warranting not just the installation, but the performance of those materials.  If they fail earlier than reasonably expected, the claim often lands with the contractor who installed them.

How long can liability last for supplied materials?

Under the CGA, the duration of the guarantees for supply materials is not explicitly time-limited. Instead, the guarantees apply for a "reasonable period" depending on the nature of the goods or services, their expected lifespan, and the circumstances of their use. For example, goods must remain of acceptable quality, durable, and fit for purpose for a reasonable time as judged by what a reasonable consumer would expect, taking into account factors such as the nature of the goods and their price.

In regard to the Building Act, the implied warranties for residential building work are enforceable for a period of 10 years, however this time period doesk not imply that all building materials must last for 10 years, only that a claim cannot be made under these implied warranties beyond this timeframe.  Instead, the focus is on whether the materials are suitable for their intended purpose and comply with all laws and legal requirements, including the Building Code. The Building Code itself specifies performance standards for building materials, such as durability requirements, which may vary depending on the type of material and its intended use.

What if the materials were supplied by the homeowner or their agent?

Legislation and case law provides that a contractor may not be liable for defects caused by factors outside their control, such as acts or omissions by others, including architects, or defects inherent in materials specified by the employer or their agent. 

Further, the contractor must have assumed responsibility for the selection of materials or if the employer must have relied upon the contractor's skill and judgement, for the contractor to be liable for ensuring that the materials are of good quality and fit for purpose.

What does this mean for contractors in practice?

The key point for contractors is simple: if you supply materials as part of residential work, the law often treats you as standing behind those materials, even if you did not manufacture or design them. Liability can arise years after the job is completed, and the cost exposure is not limited to the product itself — it can include access, removal, consequential damage, and reinstatement.

This risk cannot be avoided by contract wording alone, because the Building Act and the CGA impose non-excludable obligations. Instead, managing the risk requires practical steps, such as:

  • Carefully selecting reputable suppliers and proven products;
  • Keeping clear records of what was specified, who selected the materials, and any advice given;
  • Documenting warnings where materials are client-specified or where concerns exist;
  • Understanding warranty terms offered by manufacturers and how they operate in practice; and
  • Ensuring appropriate insurance cover is in place for defective products and resulting damage.

How can contractors reduce the risk of material-related claims?

Many contractors assume their risk ends when installation is complete and there are no workmanship issues, however in reality, responsibility for material performance can extend for years.

Being aware of this hidden exposure, and actively managing it, is essential to protecting both your business and your bottom line.

If you would like further or more specific advice on construction related issues, get in touch with Rebecca Richter, our construction law expert, or Ford Sumner’s division of Tradie Law at helpdesk@tradielaw.co.nz.

FAQs about contractor liability for supplied materials

 

1 Can a contractor be liable for defective materials they did not manufacture?

Yes. In New Zealand, a contractor who supplies and installs materials may still be liable if those materials are not fit for purpose, are defective, or do not last for a reasonable period, even if the contractor did not manufacture them.

2 What laws apply when contractors supply materials for residential building work?

The main laws are the Building Act 2004 and the Consumer Guarantees Act 1993. These laws can imply warranties into residential building contracts and create obligations relating to the quality, suitability, and durability of supplied materials.

3 How long can a contractor be liable for supplied materials?

Under the Building Act, implied warranty claims for residential building work are generally enforceable for up to 10 years. Under the Consumer Guarantees Act, materials must last for a reasonable period, depending on the type of product, its expected lifespan, and how it is used.

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