Suburb guide · 2157
Can I build a duplex or granny flat in Forest Glen?
Most of Forest Glen is land this tool does not answer for. 21 of the 21 blocks we checked sit in rural, conservation, industrial or special-purpose zones rather than a residential one, and Block Checker covers residential zones only. The counts below are what it could assess — they are not a finding that nothing can be built. For land like this, a planner reads the LEP for the zone directly.
Forest Glen sits in Hornsby Shire Council's area under Hornsby Local Environmental Plan 2013. We ran 21 real Forest Glen addresses through the checker: the typical block is 25,519 m² with 163.2 m of frontage. Most of them are not residential land, so see the note below before reading the counts.
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The typical Forest Glen block
The middle block of the 21 we checked is 25,519 m² with 163.2 m of street frontage. The smallest was 763 m² and the largest 106,570 m². Zones in the sample: RU1 (19), C3 (2).
The 21 blocks we checked, by land size.
A granny flat
0 of the 21 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 Forest Glen
0 of the 21 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.
Low and Mid-Rise
None of the 21 blocks we checked fell inside the state Low and Mid-Rise area, so in this part of Forest Glen 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
20 of 21 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 21 real Forest Glen 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 21 blocks we checked" rather than a figure for every block in Forest Glen. 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.