Using AI to Plan Your Build? Check These Five Things First
Nathan Strawbridge
Director
AI is a handy way to get your head around a build. But a quick answer and the right answer for your section aren't always the same thing.
It pays to know where the gap is before you spend money on plans.
It doesn't know what it doesn't know
Ask an AI what a new kitchen costs and you'll get a number. What you might not get is the currency, the level of spec it assumed, or the year the figure came from. Once a number is in your head, it's hard to shake. It sounds sure, but it isn't based on your council, your site or your spec.
It tends to agree with you
The way you ask shapes what you get back, and AI leans towards being agreeable. "Can I build a deck?" will probably get you a friendly yes. A better question is: "Can I build a deck over 1 metre high without a balustrade under New Zealand rules, and where does that come from?"
That one has a clear answer. The Building Code requires a barrier wherever someone could fall 1 metre or more. What trips people up is that the consent threshold is a different number, generally 1.5 metres, and most of the confusion comes from the two rules using different heights. Even a well-worded question needs checking against the source.
Rules change
The granny flat rules are a good example. Since 15 January 2026, certain new single-storey standalone dwellings of up to 70 square metres can be built without a building consent, provided the design is simple, it meets the Building Code, and the work is done or supervised by licensed building professionals. An answer drawn from older information could easily have you budgeting for a building consent that may no longer be required.
But no consent doesn't mean no rules. Homeowners must get a Project Information Memorandum (PIM) from their council before work starts and notify the council once the build is finished, and a development contribution may still apply. Resource consent is handled separately, through a national standard with its own conditions. Your site can also have limits of its own, like overlays, that a general answer may not pick up. Checking your council's planning maps takes a few minutes. It can tell you whether you're heading for a resource consent before you've paid for a single drawing.
Who's using the tool matters
AI doesn't replace expertise. It amplifies it.
The same tool in the hands of someone who understands construction, planning and compliance is very different from the same tool in the hands of someone who doesn't yet know what questions to ask.
We've been using AI in our business to help improve our internal systems. Early on, when testing it, we'd ask for things like an update on compliant balustrading and sometimes the answers weren't quite right. We could tell because we knew enough to question the answer, check the source and correct it.
That's really the point. Knowing what to ask is important, but knowing when an answer doesn't look right is just as valuable.
It's similar with licensed building practitioners (LBPs). Restricted building work covers critical parts of residential construction, including primary structure and external moisture management, and it isn't limited to work that needs a building consent. That's why even a consent-exempt granny flat still requires appropriately licensed people to carry out or supervise restricted building work.
At Our Projects, the LBPs supervising our building work are part of our own team. For our clients, that means the people responsible for delivering and supervising the work sit within the same business they've contracted to do the job.
It's a fair question to ask any builder: who is the licensed building practitioner on my job, and how are they connected to the company?
Before you trust an AI answer on your build
- Tell it where you are and what you mean. Say New Zealand, name your council, and give the size and level of spec. Ask for prices in NZD.
- Ask for the source, then read it. The Building Performance website at building.govt.nz is a good start, and its "Can I build it" tool helps you work out whether your work needs a building consent.
- Ask it to argue against your plan. "What could stop this?" gets you further than "Can I do this?"
- Check the date. If rules have changed recently, an older answer may be out of step.
- Ring us before you pay for design. A ten-minute call can often identify whether your idea could be heading towards a resource consent, development contributions or another issue worth checking before you start spending money on plans.
If you're planning a build and something doesn't sit right, jump on a call with me. Ten minutes might be all it takes to keep you on the right track.
