Suburb guide · 2234
Can I build a duplex or granny flat in Illawong?
Illawong sits in Sutherland Shire Council's area under Sutherland Shire Local Environmental Plan 2015. We ran 24 real Illawong addresses through the checker: the typical block is 732 m² with 18.3 m of frontage, 19 of the 24 could add a granny flat, and 2 could carry two separate homes today.
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The typical Illawong block
The middle block of the 24 we checked is 732 m² with 18.3 m of street frontage. The smallest was 595 m² and the largest 11,140 m². Zones in the sample: C4 (18), C2 (2), R2 (2), C3 (1), SP2 (1).
The 24 blocks we checked, by land size.
What homes sell for in postcode 2234
Median sale prices for the whole of postcode 2234, January to March 2026. These cover every suburb sharing the postcode, not Illawong alone, and they are not a value for any one block.
- Houses: $1.88m (59 sales)
- Units and apartments: $1.21m (11 to 30 sales, a small sample)
Source: NSW Government Rent and Sales Report (Department of Communities and Justice), sales tables by postcode, NSW Government. Updated each quarter.
A granny flat
19 of the 24 blocks we checked could take one. Sutherland Shire LEP cl 5.4(9) — the greater of 60 m² or 5% 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 Illawong
2 of the 24 blocks we checked could carry two or more separate homes today.
Under Sutherland Shire Local Environmental Plan 2015 a dual occupancy needs 600 m² — this LEP sets no frontage minimum, so Council's DCP governs width.
Only 2 of the 24 blocks we checked were ordinary R2 land outside the Low and Mid-Rise area, which is too few to read anything into — most of Illawong in our sample was zoned or mapped some other way.
Low and Mid-Rise
None of the 24 blocks we checked fell inside the state Low and Mid-Rise area, so in this part of Illawong 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
13 of 24 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 24 real Illawong 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 24 blocks we checked" rather than a figure for every block in Illawong. 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.