The true cost of building: what the per square metre rate leaves out

Most building budgets start with a single number: a rate per square metre. Multiply it by the floor area, add a little for luck, and you have a figure to take to the bank.

The trouble is that the number was never built to carry that much weight. MoneyHub’s guide to building costs (updated June 2026) puts the national average at $3,245 per square metre, with the Bay of Plenty at $3,431, then cautions that averages shouldn’t be relied on. As luxury home designers working from Tauranga and New Plymouth, Tony Biesiek, a Certified Passive House Designer, and our design team see that gap often, so it’s worth walking through.

What the average leaves out

Those figures come from council consent data and describe the build itself. MoneyHub notes they exclude land, driveways, landscaping, fences and earthworks such as drainage and retaining walls, and that these external items can add 30 to 50 per cent to the cost of the completed home, depending on the site’s size, contours and distance from services. Professional fees, GST and consent costs sit outside the average as well.

Council fees that vary from place to place

Council charges are the first hidden cost to understand. Does the project need a resource consent, the council’s permission for work that falls outside the district plan’s rules? Building consent fees vary widely too, because each Building Consent Authority (the council body that processes consents) sets its own. Tauranga City Council, for example, is typically more expensive than Western Bay of Plenty District Council.

Then there are development contributions, the charges a council sets to help fund the roads, water and other infrastructure a new home relies on. Like consent fees, they differ across the country, and Tony notes it’s not unusual for the figure to be north of $50,000.

The consultants behind the drawings

A new home rarely needs only a designer and a builder. Most new work needs a geotechnical investigation, which tests the ground to establish what lies beneath the site and what foundations it requires. A surveyor provides a topographical survey (a precise map of the site’s levels and boundaries) and, later, a certified building set-out that marks the home’s position accurately on the ground. A structural engineer designs the elements that hold the building up, and a civil engineer typically handles drainage, stormwater and site works. Rural sites often need an OSET design as well, meaning on-site effluent treatment, the wastewater system required where there is no council sewer. That is by no means the full list.

Why complexity matters more than size

A complex build costs more than a simple one of the same floor area, and it usually calls for more consultants. MoneyHub makes the same point: two homes of identical size can be entirely different propositions once the structure, glazing, cladding and detailing diverge. Its guide suggests a range from around $2,000 per square metre for a basic home to $5,000 or beyond for one with luxury finishes and ambitious design. Those figures describe the build alone, though.

Once all the costs above are counted, even a basic home starts at around $3,500 per square metre, and a complex, luxury-level home will come in well north of $5,000. That is a wide gap to carry on a single average.

Planning for the whole picture

This is why we ask clients to share their real budget at the very start. Our process includes a cost estimate from a quantity surveyor (the professional who measures and prices a design) or builder during the design stage, so the design is tested against the budget before we move to documentation. We then review it with you at every milestone, as we explain in your budget is our commitment. MoneyHub also suggests a contingency of around 10 per cent, rising to 20 per cent for a particularly complex or risky build. Our fees are equally open: typically 9 to 12 per cent of the approved project cost plus GST for our full service, and 7 to 10 per cent for partial service.

After more than 1,100 commissions since 2002, we’ve found that clients who are upfront about their budget arrive at the end with less stress and more satisfaction.

Give Tony a call on 0800 999404 or drop him an email at info@imaginenz.com. He’d love to grab a coffee, bring the sketch pad, and see if there’s a connection that could turn your site into your dream home.