How Much Does a House Extension Cost in Auckland? (2026)

What does each type of extension cost per square metre?

The rate depends on how much plumbing, glazing and structure the new space carries. Indicative 2026 Auckland ranges:

• A basic ground-floor room with no plumbing, such as a bedroom or study, sits toward the lower end of the $3,500 to $8,000 per square metre range.
• Open-plan living runs about $4,500 to $6,800 per square metre. The glazing and the opening into the existing house account for much of it.
• An extension with a new kitchen or bathroom runs about $5,500 to $8,000 per square metre, because wet areas bring drainage, waterproofing and more trades.

Treat these as a starting point. Two extensions of the same size can sit at opposite ends of the range because of what they connect to, what they open up and how hard the site is to get into.

A worked example: the 30sqm extension

A 30sqm ground-floor extension in Auckland comes in at roughly $135,000 to $204,000 at open-plan living rates. That is enough for a generous family room, or a kitchen and dining space opening to the garden.

Fees are a separate line. Architect fees for an extension of around 50sqm commonly run $5,000 to $12,000, with engineering, council fees and any surveying on top. Hold a contingency as well, nearer 20 percent on a pre-1940s home, because the join between new work and an old house is where the unknowns are.

The rate also assumes reasonable access. A steep section, a narrow driveway or a back garden only a wheelbarrow can reach adds time to every delivery and every trade. So does the work on the existing house: an opening cut through an external wall, a roof tied into the old one, floors brought level, and the rooms either side made good.

How much more does a second-storey extension cost?

A second storey typically costs 10 to 30 percent more than the equivalent ground-floor rate, or about $5,500 to $7,500 per square metre. The uplift pays for structure: the existing walls and foundations have to carry the new floor, and engineering often calls for strengthening below.

Going up also means scaffolding, a stair that takes floor area from the level below, and a roof that comes off and goes back on while the house stays weathertight. In return you keep the garden, which on a tight Auckland section can be worth more than the uplift.

Consent and the overlay check

Almost every house extension needs a building consent, so budget for council fees and allow time for processing. Some also need resource consent, and that is the one to check early.

Many Auckland villas and bungalows sit under the Special Character Areas overlay or a heritage overlay, which can require resource consent for additions. The rules are changing, so check your address on Auckland Council's Unitary Plan viewer and talk to a planner before you commit to a design.

Should you extend or move?

Extending usually makes sense when you like the street, the school zone and the bones of the house, and the only thing wrong is space. Compare the full extension cost, fees and contingency included, with the price gap between your home and one that already has what you need. Selling and buying has its own costs, and the new house may still need work.

Extensions we have built

In Remuera, a renovation and addition delivered a new white kitchen and open-plan living that opens through full-height sliders to a covered outdoor room among the trees. At Rawhitiroa in Kohimarama, a 60sqm extension added a gym and room for a bigger kitchen and dining area, and the project won the 2023 National Supreme Renovation of the Year.

If the extension includes a bathroom, our bathroom renovation cost guide covers what wet areas add. For how we plan and price this work, see house extensions, or Talk to Finn about the space you need.