RemodoGranny flats (secondary dwellings) in NSW: size, rules & approval
A granny flat — formally a 'secondary dwelling' — is a self-contained home on the same lot as a main house. In NSW many can be approved quickly as complying development. Here's what the state rules generally require, and where to check your own block.
What counts as a secondary dwelling
A secondary dwelling is a self-contained dwelling that is on the same lot as, and is subordinate to, the principal home. It has its own kitchen, bathroom and living space, and can be attached to the main house or stand alone.
Under the NSW Housing SEPP, the internal floor area of a secondary dwelling is generally capped at 60 m² (unless another planning instrument applying to the land allows more). The combined floor-space calculation typically includes the principal dwelling, the secondary dwelling and attached structures like garages, carports, patios, decks and verandahs.
Site requirements you usually need to meet
To be built as complying development, a secondary dwelling generally needs to sit on a lot of at least 450 m², with a minimum width around 12 m at the building line of the existing dwelling. Common setback standards are about 3 m from the rear boundary and 0.9 m from side boundaries, though these depend on lot size and the applicable code.
Secondary dwellings are generally permitted in residential zones (for example R1, R2, R3, R4 and R5). Site-specific controls — flooding, bushfire, heritage, easements — can change what's allowed, so the standards above are a starting point, not a guarantee.
How approval works
There are two main routes. A Complying Development Certificate (CDC) is a fast-track combined planning-and-construction approval assessed against the coded standards — it can be issued by a private certifier or council, sometimes in as little as around 20 days, if your proposal meets every standard.
If your project doesn't fit the codes (for example it's larger than allowed, or the site has special controls), you'll need a Development Application (DA) to council instead, which is assessed with more discretion and may involve neighbour notification.
Can you rent it out?
Yes — in NSW a secondary dwelling can generally be rented out, which is why granny flats are popular for rental income or multi-generational living. You still need the right approvals in place first, and the building must meet safety requirements.
Frequently asked
How big can a granny flat be in NSW?＋
Generally up to 60 m² of internal floor area under the Housing SEPP, unless a local planning instrument allows more.
What size block do I need?＋
To use the complying development pathway, the lot is generally required to be at least 450 m² with about 12 m width at the building line.
How long does approval take?＋
A complying development certificate can be issued in as little as ~20 days when the proposal meets all the coded standards. A DA takes longer as it involves council assessment.
Can I rent out my granny flat?＋
Yes, secondary dwellings can generally be rented in NSW, provided you have the required approvals and meet building-safety rules.
See it on your own block
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This content is general information only and is not planning, legal or professional advice. While we aim to keep these guides accurate and current, planning laws change frequently and vary by state, council/LGA, zone and site-specific controls (flooding, bushfire, heritage, easements and more). Figures quoted are indicative and may be out of date.
Remodo makes no warranty as to the accuracy, completeness or currency of this information and accepts no liability for any loss arising from reliance on it. Always confirm the requirements for your specific property with your local council or the relevant state planning portal, and seek advice from a qualified planner, certifier or lawyer before making decisions or starting work.