Why everyone quotes per square metre
Cost per square metre is the quickest way to compare building prices: total build cost divided by floor area. It is useful for an early budget. It is also easy to misuse, because two figures can measure very different things — one might include the garage and site works, another only the house on a flat, prepared lot.
Before comparing any per-square-metre figure, ask what area it is measured over and what it includes.
The published NSW average
Master Builders NSW reported in May 2026 that New South Wales is the most expensive jurisdiction in the country to construct a detached house, at an average of $2,396.23 per square metre, with the average cost of a new detached house in NSW at $565,749 in 2024/25.
That is a statewide average across all detached houses, including high-volume project homes on flat estate lots. It is a sensible benchmark for the market, not a price for a specific custom home in Sydney. A custom design, a knockdown rebuild site or a higher specification can sit well above it.
What area is being measured?
Builders may measure gross floor area including the garage, alfresco and porch, or only the internal living area. A 300 m² figure that includes a double garage and alfresco is a very different house from 300 m² of internal living space. Garages and covered outdoor areas cost less per square metre to build than kitchens and bathrooms, so including them lowers the average figure without lowering the price.
What pushes the figure up or down
Wet areas: kitchens, bathrooms, ensuites and laundries are the most expensive rooms per square metre. More of them means a higher rate. Storeys and structure: double-storey homes need stairs, structural floors and scaffolding; large open spans, voids and big glazed openings need more steel and engineering. Ceiling height: higher ceilings add framing, plasterboard, windows and heating and cooling volume.
Shape and roof: a simple rectangular footprint with a simple roof is cheaper per square metre than one with many corners, cantilevers and roof planes. Finishes: stone, joinery, tapware, flooring and appliance choices can move the rate significantly in either direction.
Site costs sit on top
Most per-square-metre figures describe the house, not the land it sits on. Slope, soil classification, retaining walls, rock, drainage, service connections, demolition on a rebuild, driveways and landscaping are often extra. On a difficult site these can be a large share of the total.
A contour survey and soil test before pricing let these be fixed in the contract rather than left as allowances.
Size isn’t linear
Smaller homes usually cost more per square metre than larger ones, because the expensive rooms — kitchen, bathrooms, laundry — don’t shrink in proportion. Adding a bedroom to a plan adds relatively cheap floor area; adding a bathroom adds expensive area. That is one reason a compact, well-planned home can cost more per square metre while costing less overall.
Using cost per m² properly
Use the published average to sense-check early ideas, not to set a budget. To get a reliable number, settle the brief, get the site investigations done, choose an inclusions level, and ask for a fixed price that lists what is and isn’t included. Then compare quotes on identical drawings and inclusions.
Sources
Master Builders NSW — Average costs of building Australian homes (May 2026): https://www.mbansw.asn.au/media/industry-news/average-costs-building-australian-homes
NSW Government — Contracts for residential building work: https://www.nsw.gov.au/housing-and-construction/building-or-renovating-a-home/preparing/contracts