A granny flat, known in the planning rules as a secondary dwelling, is one of the most popular home projects in Sydney. It can house a parent, give grown-up children some independence, or bring in rental income. The rules are friendlier than many people expect, but there are a few things every block needs to get right.
The basics
Under the NSW state rules for complying development, a granny flat is generally limited to around 60 m² of floor area and must be on the same lot as the main house. For the fast-track CDC pathway, the lot generally needs to be at least 450 m² and around 12 m wide at the building line. These are general figures: your council's controls, and the current version of the rules, decide what applies to you.
Granny flat quick check (NSW, general guide)
| CDC (fast track) | DA (council) | |
|---|---|---|
| Who approves | Private or council certifier | Council |
| Typical timeframe | Generally a few weeks | Generally a few months |
| Flexibility | Must meet every standard | Merit based, variations possible |
| Lot | Generally 450 m²+ and about 12 m wide | Per council LEP and DCP |
| Good for | Standard, unconstrained blocks | Smaller, sloping or constrained sites |
Timeframes and minimums vary. We confirm the current controls for your address.
Common issues we see
Sewer mains in the backyard
The backyard is often where Sydney Water's sewer main runs. Building over or close to it has rules, and it can push the granny flat to a different spot. Get the sewer diagram early.
Access to the granny flat
There needs to be a sensible path from the street. On narrow blocks with the main house close to both side boundaries, this takes some planning.
Setbacks and privacy
Side and rear setbacks increase with height. A single-storey granny flat close to the rear boundary is often fine, but windows facing neighbours need thought.
Trees and landscaping
The site still needs a minimum amount of landscaped area and private open space for the main house. Large trees can limit where the flat can go.
Bushfire, flood and heritage
These can rule out the CDC pathway and mean a DA is needed, even for a modest granny flat.
What goes into a granny flat drawing set
Typical documentation
- Site plan with setbacks and sewer position
- Floor plan and roof plan
- Elevations and a section
- Landscape and open space calculations
- Stormwater concept
- BASIX certificate
The takeaway
Most granny flats are straightforward when the site is checked first. Send us your address and we'll tell you whether a CDC is likely to work or whether a DA is the better path, and where on the block the flat can realistically go.
Talk to Sam, our Marketing & Operations ManagerStart with your address
Send us your address and what you'd like to do. We'll check the zone, the lot and your council's controls, and come back with the likely approval path and a fee proposal. Every project is quoted on its own.