The ABS average for a new house in Western Australia was $407,114 in 2024-25, the lowest of the mainland states, on an average floor area of 257 square metres. That figure covers every builder and finish level in the state, so it is a floor for a project home rather than a guide to a custom or energy-efficient build. Quantity surveyors put custom-built dwellings in Perth at $3,100 to $5,100 per square metre excluding GST.
Bracen’s guide to the cost to build a house in Australia lays those numbers out by state and by build quality, with the sources and dates attached. It is a good starting point before you talk to us about a SIP home in Perth, where structural insulated panel construction changes where the money goes: more in the shell, with the energy performance designed in from the start.