Suburb guide · 2080
Can I build a duplex or granny flat in Mount Kuring-Gai?
Mount Kuring-Gai sits in Hornsby Shire Council's area under Hornsby Local Environmental Plan 2013. We ran 25 real Mount Kuring-Gai addresses through the checker: the typical block is 914 m² with 18.4 m of frontage, 22 of the 25 could add a granny flat, and 10 could carry two separate homes today.
Thinking of building or selling in Mount Kuring-Gai?
Tell us what you have in mind and we'll read your block and come back to you within a day. Free, no obligation.
The typical Mount Kuring-Gai block
The middle block of the 25 we checked is 914 m² with 18.4 m of street frontage. The smallest was 500 m² and the largest 28,140 m². Zones in the sample: R2 (23), E4 (1), C3 (1).
The 25 blocks we checked, by land size.
A granny flat
22 of the 25 blocks we checked could take one. Hornsby LEP cl 5.4(9) — the greater of 60 m² or 33% of the house’s total floor area, parking excluded. Separately, the state Housing SEPP allows a granny flat of up to 60 m² through the ten-day complying-development route on a lot of 450 m² or more with a 12 m frontage, where the land is not flood, bushfire or heritage constrained.
Dual occupancy (duplex) rules in Mount Kuring-Gai
10 of the 25 blocks we checked could carry two or more separate homes today.
Under Hornsby Local Environmental Plan 2013 a dual occupancy needs 700 m² and 16 m of frontage.
Of the 23 ordinary R2 blocks in our sample sitting outside the Low and Mid-Rise area — where that minimum is the only test that applies — 14 had the frontage and 14 had the land. 10 had both.
Both tests bite here in roughly equal measure, so a block needs to be unusual on two counts at once. That is why the number clearing them is small.
Low and Mid-Rise
None of the 25 blocks we checked fell inside the state Low and Mid-Rise area, so in this part of Mount Kuring-Gai the LEP minimums are what count. The boundary is a walking distance from a listed centre, so it can cut through a suburb — the checker reads which side of it your own address sits on.
What else turned up
17 of 25 were on bushfire-prone land. Any of those takes a block out of the fast-track routes and into a full DA, so it changes the answer more than the lot size does.
How we got these numbers
We took 25 real Mount Kuring-Gai street addresses from the NSW geocoder and ran every one through the same engine this site runs for you, reading the planning controls live. Nothing here is modelled or estimated.
It is a sample, not a census. The addresses are a spread across what the geocoder returns, so treat these as "of the 25 blocks we checked" rather than a figure for every block in Mount Kuring-Gai. Your own block is the only one that answers for itself — that is what the box on the right is for.
Enter the address — lot, frontage, zone, constraints and what it can carry.