Granny Flat Size and Setback Calculator

Maximum sizes vary by state. NSW caps CDC-approved granny flats at 60sqm under NSW SEPP. WA allows ancillary dwellings up to 70sqm without planning approval under R-Codes 2022. Victoria covers small second homes up to 60sqm under the 2023 permit-free pathway. Queensland (Brisbane City Plan) allows secondary dwellings up to 80sqm as Accepted Development on standard lots. Larger builds in any state require a DA or planning permit from council.

A setback is the minimum distance a building must be placed from a boundary — side, rear or front. Setback rules exist to protect privacy, natural light and access for neighbouring properties. If your granny flat does not meet the required setbacks for your state, you cannot use the fast-track approval pathway (CDC, Building Permit or Accepted Development) and will need to apply for a DA or variation through council instead.

In NSW, the minimum lot size for a CDC granny flat is 450sqm under NSW SEPP (Exempt and Complying Development Codes) 2008. The lot must also be at least 12m wide at the building line. If your lot is under 450sqm or under 12m wide, you cannot use the CDC pathway and will need a Development Application (DA) through your local council. Use the calculator above to check how your lot measures up.

No — under R-Codes 2022 reforms, WA removed the minimum lot size requirement for ancillary dwellings. Compliant granny flats up to 70sqm can now be built on any residentially zoned lot, regardless of size, without planning approval. You will still need a Building Permit and must meet R-Code setback requirements. This makes WA one of the most flexible states for granny flat development in Australia.

No — all states require minimum setbacks from side and rear boundaries. In NSW, the minimum side setback is 0.9m for single-storey builds and 1.9m for anything over 3.8m high, with a 3m minimum rear setback. WA requires 1m to 1.5m side setbacks depending on lot width. VIC requires 1m side and 3m rear setbacks under ResCode. QLD (Brisbane) requires 1.5m side setbacks. Building too close to a boundary without a variation from council is not permitted under any fast-track pathway.

Yes — but you will need a Development Application (DA) or planning permit rather than the fast-track pathway. Councils can approve larger secondary dwellings at their discretion, but the process takes significantly longer and is not guaranteed. In practice, most granny flat builders recommend keeping the build within the state maximum to avoid council delays and additional costs. Talk to your local council or a town planner if you want to explore a larger build.