A kit granny flat saves roughly a quarter on the building part if you manage the trades yourself. For a 60 m² two-bedroom flat in Melbourne that means about $132,000–$198,000 all-in, against $176,000–$255,000 for a builder’s turnkey price.
Both include GST, design, permits, connections and basic landscaping. The kit column assumes you hire and manage the trades yourself.
| City | Kit, you manage trades | Builder, turnkey | Difference |
|---|---|---|---|
| Melbourne | $132,000–$198,000 | $176,000–$255,000 | about $51,000 |
| Sydney | $145,000–$219,000 | $194,000–$285,000 | about $58,000 |
| Brisbane | $119,000–$181,000 | $158,000–$231,000 | about $45,000 |
| Perth | $119,000–$185,000 | $158,000–$237,000 | about $46,000 |
A kit is the frame, roof, cladding, windows and doors, delivered. Supply-only kits for 45–60 m² run about $20,000 to $60,000. The slab, plumbing, electrical, kitchen, bathroom, linings, painting and flooring are all still to come, and they are most of the cost.
Usually by about a quarter on the building part. For 60 m² in Melbourne that is about $132,000–$198,000 all-in for a kit you manage, against $176,000–$255,000 turnkey.
Supply-only kits for 45–60 m² run about $20,000 to $60,000. That is the frame, roof, cladding, windows and doors, not a finished home.
In most states, yes, if you manage the build yourself. Check with your state building authority before you buy a kit.
Design, permits, the surveyor or certifier, water, sewer and power connections, and site problems like slope or a sewer pump. Together these are often $20,000 to $50,000.
If you have time, can manage trades and the block is easy, it can save $40,000 or more. If not, delays and mistakes can eat the saving.
Put this price and your expected rent into the rent and ROI calculator to see the yield and payback time.
Prices are all-in estimates including GST, from our cost calculator, which is built on 2026 builder price lists and cost guides. Checked 25 October 2026. Get at least two quotes after a site visit.