I Have an Exemption From Building Consent – Why Do I Still Need an Engineer?

It is a question we hear regularly at Branch Consulting: “The council says my project does not need building consent, so why would I pay for an engineer?” It sounds logical on the surface – if the building consent authority does not require it, surely it is fine, right?

Not quite. Let us unpack what a building consent exemption actually means, and why getting engineering input anyway can save you a lot more than it costs.

What Does Building Consent Exemption Actually Mean?

Under Schedule 1 of the Building Act 2004, certain low-risk building work is exempt from the requirement to obtain building consent. Common examples include:

• Single-storey detached sheds or sleepouts under 30m2 (with conditions)
• Ground-floor verandas and awnings
• Low retaining walls (under 1.5m in most cases)
• Minor structural repairs and maintenance
• Certain fences and decks

The exemption means the council will not check your plans or inspect your work. It does not mean the work is exempt from the Building Code. The Building Code still applies in full – you just do not have a council officer checking compliance.

The Risk You Are Carrying

Here is the crux of it: if you build something that does not comply with the Building Code – even if it is exempt from consent – and it later fails, you are personally liable. Your insurance may not cover it. And if your structure damages neighbouring property or injures someone, the costs can be devastating.

We have seen cases in Christchurch where exempt retaining walls failed in heavy rain, causing thousands of dollars in damage to the property below. The homeowner who built it without engineering input was fully exposed.

When an Engineer Makes Sense for Exempt Work

1. Retaining walls near boundaries

A wall under 1.5m might be exempt, but if it is on a boundary or supporting surcharge (driveways, buildings, fill), it needs proper design. A failed wall can trigger a landslide onto your neighbour’s property – and that is not an exempt problem.

2. Decks with fall risk

Ground-floor decks can be exempt, but if they are more than 1m above ground, the risk changes. A failed deck joint can cause serious injury, and your insurance company will ask who designed it.

3. Sleepouts and sheds on reactive ground

If you are building on TC2 or TC3 land in Christchurch, even a small sleepout needs proper foundations. The ground moves differently here than in most of New Zealand, and a standard slab on reactive ground can crack within months.

4. Renovations that alter load paths

Removing a non-loadbearing wall sounds simple, but sometimes those walls are doing more work than they appear to. A quick site visit from a structural engineer costs a few hundred dollars – far less than fixing a sagging roof.

What an Engineer Actually Provides

For exempt work, you do not need a full Producer Statement (PS1) – but you can still get:

• A site-specific assessment and recommendations
• Design sketches or details you can give your builder
• Confirmation that your proposed work meets the Building Code
• Peace of mind that it will not cause problems down the track

Most of our clients who start with “do I really need an engineer?” end up glad they asked. It is not about ticking boxes for council – it is about building something that lasts.

The Bottom Line

Building consent exemption is permission from the council to self-certify your work. It transfers the compliance risk from the council to you. If you are confident in your understanding of the Building Code and ground conditions on your site, go ahead. If you are not – and most homeowners are not – a few hours of engineering time is cheap insurance.

Got an exempt project you are unsure about? Give us a call and we will talk you through what you actually need.