Granny flat checker · NSW
Can I get a granny flat on my site?
Answer the questions on the left. The panel on the right tells you whether a granny flat is likely, whether it is CDC or DA, and whether drainage is going to be the thing that bites. Nothing is sent anywhere — it runs in your browser.
A guide, not an approval. The CDC tests are from the State Environmental Planning Policy (Housing) 2021, Chapter 3 and Schedule 1, and the Codes SEPP constraint screen (cl 1.17A–1.19); drainage rules are set council by council. Lot size and frontage are the figures on your deposited plan, not the rates notice’s rounding. The free site check confirms everything against the Planning Portal and your title.
The four things that decide it
Is it permitted? A secondary dwelling is permitted with consent on a lot in a residential zone where a house is permitted, and there must be one principal house on the lot — and only one granny flat (Housing SEPP 2021, Chapter 3).
CDC or DA? A private certifier can approve a granny flat as complying development when the lot is at least 450 m², has 12 m of frontage (15 m over 900 m², 18 m over 1,500 m²) or a 3 m battle-axe handle with a 12 m × 12 m building area, and is not a heritage item or environmentally sensitive land (Housing SEPP Schedule 1 cl 2; Codes SEPP cl 1.17A). Fail one of those and it is a DA to council, assessed on merit — slower, but a granny flat on a 400 m² lot is approved every week.
Will it fit? Within the CDC standards the flat is up to 60 m² (some LEPs allow more), up to 8.5 m high, 0.9 m off the side boundary and 3 m off the rear on a 450–900 m² lot, with 24 m² of private open space left for the house (Schedule 1 cl 9, 10, 17). Two storeys pushes the side and rear setbacks out by three times the height over 3.8 m — which is why most over-garage flats on small lots end up as DAs.
Where does the water go? This is the one people miss. A certifier cannot issue a CDC unless stormwater reaches a lawful point of discharge — the street, a council pipe, or a registered inter-allotment easement. If the back of your block is lower than the street and there is no easement over the downhill neighbour, you need their agreement to create one (Conveyancing Act s88B), a Supreme Court order (s88K) as a last resort, or whatever your council permits instead: a charged (pump-up) line, an absorption trench, or a pump-out system. Some councils allow all three with conditions; some allow none. Find this out before you fall in love with a design.
Read more in our granny flat rules NSW guide and CDC vs DA.
Can you build a granny flat on your block?
Send us the address. We check it against the NSW controls and tell you what fits, which pathway applies and what it will cost — free, within one business day.