Dual occupancy rules in Australia
A dual occupancy - commonly called a duplex - is two dwellings on a single lot, either attached or detached. Unlike a granny flat there is no single national rule: whether you can build one is decided by the zone your property sits in, the minimum lot size and frontage mapped to it, and your local planning instrument. This guide sets out what controls the answer in each state and territory, and the indicative numbers to test your block against.
The short version
- Two things decide it: whether your zone permits dual occupancy at all, and whether your lot meets the minimum lot size and frontage mapped to that property.
- Indicative minimum lot sizes run from roughly 400 m² to 800 m² nationally, but the figure that binds is the one mapped to your address, not a state average.
- NSW made the clearest change: since 1 July 2024 dual occupancies have been permitted with consent in every R2 low density residential zone across NSW, other than in Bathurst Regional, Hawkesbury, Blue Mountains and Wollondilly. Victoria added a 10 business day VicSmart pathway from 16 October 2025 and the ACT opened RZ1 and RZ2 to duplexes from 1 July 2026.
- Building two dwellings and creating two separate titles are different approvals. Some states allow Torrens or strata subdivision afterwards, others only let the two dwellings be sold together.
- Heritage listing, flood, bushfire and similar overlays commonly remove the fast-track pathway, push the proposal into full assessment, or rule it out.
Dual occupancy rules by state
Frameworks differ across Australia. Pick your state for the size limits, setbacks, approval pathway and FAQs — then check your address for overlays.
Usually yes, if the block is big enough. Since 1 July 2024 dual occupancies have been permitted with consent in every R2 low density residential zone across NSW, with four council areas excepted - but the minimum lot size and frontage mapped to your property still decide whether a specific block qualifies.
Dual occupancy rules in NSW →Usually yes, with a planning permit. Victoria sets no statewide minimum lot size for a second dwelling, but the mandatory minimum garden area and the Townhouse and Low-Rise Code standards mean most successful dual occupancies sit on lots of roughly 500 m² or more.
Dual occupancy rules in VIC →It depends on your council. Queensland has no statewide dual occupancy rule - each local government planning scheme decides which zones allow a duplex, what minimum lot size and frontage apply, and whether it is accepted, code assessable or impact assessable development.
Dual occupancy rules in QLD →Often yes. The Planning and Design Code treats two homes on one allotment as semi-detached dwellings, a group dwelling or a residential flat building, and each zone sets a minimum site area and frontage per dwelling - so the zone and the numbers mapped to your allotment decide it.
Dual occupancy rules in SA →It comes down to your R-code. Two dwellings on one lot are grouped dwellings under the Residential Design Codes, and the density code mapped to your lot - R20, R30, R40 and so on - sets the average and minimum site area per dwelling, which is what decides whether your block can take two.
Dual occupancy rules in WA →Usually yes, with a planning permit. The Tasmanian Planning Scheme allows multiple dwellings in the General Residential Zone, and the acceptable solution is 325 m² of site area per dwelling - so a lot of about 650 m² or more will normally support two dwellings.
Dual occupancy rules in TAS →Yes in most suburban areas, following a major change. The Missing Middle Housing reforms commenced on 1 July 2026 and allow duplexes, triplexes, terraces and townhouses of up to two storeys in RZ1 and up to three storeys in RZ2, removing the previous 800 m² minimum block size for a second dwelling in RZ1.
Dual occupancy rules in ACT →It depends entirely on your zone. Dual occupancy was removed from Zone SD (Single Dwelling Residential) in 2017 and has not returned, but a dwelling-group of fewer than five dwellings is a permitted use in Zone LR (Low Density Residential) and in the low-medium, medium and high density residential zones.
Dual occupancy rules in NT →Frequently asked questions
What size block do I need for a duplex in NSW?
There is no single figure. Most councils map a minimum lot size for dual occupancy between 450 m² and 600 m², and in mapped low and mid-rise housing areas a 450 m² lot at least 12 m wide cannot be refused on lot size grounds. Some councils, including Hornsby and Ku-ring-gai, require 700 m² or more. Check the minimum lot size mapped to your address before you buy or design.
What is the minimum land size for a dual occupancy in Victoria?
There is no statewide minimum. What binds is the mandatory garden area - 25 to 35 percent on lots over 400 m² - plus setbacks, private open space and car parking under the Townhouse and Low-Rise Code. In practice most dual occupancies are built on lots of about 500 m² and up, although well-designed schemes do succeed on smaller lots in the General Residential and Residential Growth zones.
What size block do I need for a duplex in Queensland?
It depends on your council. Brisbane and Rockhampton allow dual occupancy from 400 m² in their low-medium density residential zones, while other schemes require 600 m², 800 m² or more, and some only treat a duplex as accepted development at 800 m² with a 20 m frontage. There is no statewide figure - check the minimum lot size in your council's planning scheme for your zone.
What size block do I need for a duplex in Perth?
Divide the lot area by the average site area for your R-code. At R20, where the average is 450 m² per dwelling, you generally need about 900 m²; at R30 (average 300 m²) about 600 m²; at R40 (average 220 m²) about 440 m². If your lot falls under the average needed for two dwellings it will not support a duplex unless a split code or a specific scheme provision applies.
What size block do I need for two houses in Adelaide?
It depends on the zone and the Technical and Numeric Variation mapped to your allotment. In the General Neighbourhood Zone a semi-detached dwelling commonly needs about 300-400 m² of site area and 9-10 m of frontage per dwelling, so roughly 600-800 m² in total. Look your allotment up on SAPPA to see the exact figures that apply.
What size block do I need for two units in Tasmania?
In the General Residential Zone the acceptable solution is 325 m² of site area per dwelling, so about 650 m² for two. A smaller lot is not automatically ruled out - the performance criteria allow a lesser site area where infrastructure can cope and either the density suits the surrounding area or the project delivers a significant social benefit close to services.
Related building rules
This page summarises statewide rules for general guidance only and is not professional planning advice. Requirements vary by council and change over time — always confirm with your local council or a qualified planner. Last reviewed: July 2026.
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