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Dual occupancy or granny flat — which second dwelling can you build?
| Secondary dwelling | One principal dwelling plus one secondary dwelling on the same lot; the lot cannot be subdivided[1] |
|---|---|
| Dual occupancy | Two dwellings on one lot; subdivision permitted in R1, R2 and R3 zones under the low and mid-rise standards[2] |
| Secondary dwelling floor area | Commonly capped at 60 m²[3] |
| Dual occupancy lot size | Minimum 450 m² as a non-discretionary standard in low and mid-rise housing areas[2] |
| Where dual occupancy is permitted | R2 low density residential zones state-wide since 1 July 2024[4] |
| *The non-discretionary standards apply only inside mapped low and mid-rise housing areas. Permissibility and standards are two separate questions — see below. | |
In New South Wales a granny flat, or secondary dwelling, means one principal dwelling and one secondary dwelling on the same lot, commonly capped at 60 m², and the lot cannot be subdivided.[1][3] A dual occupancy is two dwellings on one lot, permitted with consent in R2 low density residential zones state-wide since 1 July 2024, with a minimum lot size of 450 m² in low and mid-rise housing areas, and subdivision is permitted in R1, R2 and R3 zones.[2][4]
Most people who set out to put a second home in their backyard start with the word "granny flat" and never learn there is a second option. In New South Wales planning language, a granny flat is a secondary dwelling, and a secondary dwelling is legally tied to the house in front of it forever. The alternative is a dual occupancy — two dwellings on one lot, which in much of NSW can now be split onto two separate titles and sold apart.
That single difference reorganises the entire project: the size you can build, the approval you apply for, the way a lender values the result, and whether you end up with one asset or two. This guide sets the two pathways side by side, and then looks at what each means when the second dwelling is built in a factory.
The difference in one sentence §
A lot with a secondary dwelling on it cannot be subdivided, and the development can only ever produce one principal dwelling and one secondary dwelling on the site.[1] A dual occupancy, by contrast, can be subdivided in the R1, R2 and R3 zones under the low and mid-rise standards, at a minimum of 225 m² and 6 metres of width per new lot.[2]
Everything else follows from that. The secondary dwelling is an addition to your property. The dual occupancy is potentially a second property.
What a secondary dwelling is §
A secondary dwelling is a self-contained dwelling within, attached to, or separate from another dwelling on the same site. It is permitted in the residential zones R1, R2, R3, R4 and R5, and councils may allow it in other zones through their local environmental plan.[1]
The size limit most commonly quoted across NSW is 60 m² of floor area, on a lot of at least 450 m², with one secondary dwelling per property.[3] For the fast complying development pathway, the Housing SEPP requires a lot of at least 450 m², with an exception where the secondary dwelling sits entirely inside an existing dwelling house.[1] If your land is smaller than that, the complying development route closes and you are back to a development application assessed by council on its merits.
Two details that surprise people: a single complying development certificate can cover a new principal dwelling and a new secondary dwelling together, and the Housing SEPP itself does not require you to add parking for the secondary dwelling — although any existing consent on your property might, and removing an existing space can create a problem.[1]
On bushfire-prone land the picture changes again. Additional requirements apply, and where the land is classified as at risk of ember attack or exposure to flames from a fire front, complying development is not available at all.[5]
What a dual occupancy is §
A dual occupancy is two dwellings on one lot. Since 1 July 2024, dual occupancies and semi-detached dwellings have been permitted with consent in R2 low density residential zones across the whole of New South Wales — the ordinary suburban house zone.[4] Semi-detached dwellings are the side-by-side version subdivided down the middle so each house sits on its own lot.[4]
Being permitted is not the same as being easy. Permissibility says council must consider your application; it does not tell you what standards apply. That second question is answered by the non-discretionary development standards, and those only operate inside mapped low and mid-rise housing areas.
Where the generous standards actually apply §
A low and mid-rise housing area is residential zoned land within 800 metres walking distance of a nominated town centre or the entrance of a nominated train, metro or light rail station, across metropolitan Sydney, the Central Coast, the Illawarra-Shoalhaven and the Lower Hunter.[4] Inside those areas, the standards for dual occupancy are a minimum lot size of 450 m², minimum lot width of 12 metres, a maximum floor space ratio of 0.65:1, a maximum height of 9.5 metres, and one car space per dwelling.[2]
Non-discretionary standards are also called non-refusal standards. If your proposal meets them, the consent authority cannot refuse the application on the ground that it fails an equivalent standard in the local environmental plan or development control plan. They apply where they are more generous than the local controls; where the local plan is more generous, the local plan wins.[4] Every other planning control continues to operate as normal.
The policy does not apply to a long list of constrained land: bushfire prone land, certain flood prone land, coastal wetlands, littoral rainforest, coastal vulnerability areas, land near dangerous goods pipelines, land under high aircraft noise, land inside a Transport Oriented Development area, heritage items, the Hawkesbury, Blue Mountains and Wollondilly local government areas, and the Bathurst local government area.[4]
Side by side §
| Question | Secondary dwelling | Dual occupancy |
|---|---|---|
| Can the land be subdivided? | No[1] | Yes in R1, R2 and R3 under the low and mid-rise standards, min 225 m² per lot[2] |
| Typical floor area limit | 60 m²[3] | Set by floor space ratio, max 0.65:1 in low and mid-rise areas[2] |
| How many dwellings result | One principal plus one secondary[1] | Two dwellings[2] |
| Minimum lot for the fast pathway | 450 m² for complying development[1] | 450 m² as a non-refusal standard in low and mid-rise areas[2] |
| Where permitted | R1 to R5 residential zones[1] | R2 zones state-wide since 1 July 2024[4] |
| Parking required by the state instrument | None additional[1] | One space per dwelling in low and mid-rise areas[2] |
Why subdivision is the decision that matters §
If you want a place for a parent, a returning adult child, or a rental you intend to hold alongside your own home, a secondary dwelling does the job and does it with the simpler approval. It stays on one title, one set of rates, one insurance policy over the property.
If your intention is ever to sell one of the two homes, a secondary dwelling cannot deliver it. No amount of building quality converts it into a saleable separate property later. That is a design decision made at the very start, not a problem you can solve at the end, and it is the single question worth resolving before you talk to any builder.
It also affects finance. A secondary dwelling is an improvement valued as part of your existing property. Two dwellings on two titles are two securities. We cover how lenders treat off-site construction in financing a modular home and financing a granny flat, and the tax consequences of renting a second dwelling in renting out a granny flat and capital gains tax.
What this means for a factory-built second home §
Most of the modular and transportable market is built around the secondary dwelling. Standard designs cluster at or under 60 m² because that is the number the NSW rules produce, and because the same footprint travels on a truck without an oversize permit. If you are building a granny flat, the factory catalogue is deep.
A dual occupancy is a different product. Two dwellings sized by a floor space ratio rather than a fixed cap are usually larger, often attached, and frequently two storeys — which pushes a volumetric builder toward multiple modules per dwelling, more crane time and more on-site connection work. That does not make off-site construction a poor fit; several Australian manufacturers build attached and multi-dwelling housing. It does mean the price per square metre and the delivery logistics look nothing like a backyard studio, and the quotes are not comparable. See delivery, transport and craneage and site works for the cost categories that scale with module count.
One more practical point. Where dual occupancies are newly permitted with consent, the complying development pathway under the Low-Rise Housing Diversity Code becomes available for them, provided the proposal meets the standards in that code.[4] For a factory builder, a complying development certificate is worth a great deal: it makes the approval date predictable, and a predictable approval date is what lets a factory hold a production slot for you.
Other states §
The terms travel badly. "Dual occupancy", "secondary dwelling", "ancillary dwelling" and "granny flat" carry different definitions and different subdivision rules in each state, and the 800-metre walking catchment model described here is a New South Wales construct with no equivalent elsewhere. Our state-by-state coverage of the secondary dwelling rules is at granny flat rules and approvals by state.
What is not covered here §
This guide does not set out dual occupancy rules for Victoria, Queensland, Western Australia, South Australia, Tasmania, the ACT or the Northern Territory. Those jurisdictions are not covered by the sources compiled here, and the NSW figures above must not be read across to them.
It does not tell you whether your own address sits inside a low and mid-rise housing area. The department publishes indicative maps, but states plainly that those maps are not legislative, cannot account for individual property constraints or local walking networks, and should not be used to make planning decisions — landowners need to check the requirements in the legislation for a specific property.[4]
It does not cover manor houses, terraces, multi-dwelling housing or residential flat buildings, which have their own standards under the same policy. It does not cover the cost of either option; published price guidance for secondary dwellings is collected in granny flat costs in New South Wales. And it does not address strata subdivision, community title, or the process of registering a new lot, which are conveyancing and surveying matters rather than planning ones.
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References §
- NSW Department of Planning, Housing and Infrastructure — Secondary dwellings under the Housing SEPP — permitted in residential zones R1 to R5; a lot on which a secondary dwelling is constructed cannot be subdivided; development can only result in one principal dwelling and one secondary dwelling on the site. A single complying development certificate can cover both dwellings. Complying development requires a lot of at least 450 m², except where the secondary dwelling sits entirely within an existing dwelling house. No additional parking is required under the Housing SEPP. planning.nsw.gov.au/the-planning-system/housing/housing-sepp/secondary-dwellings
- NSW Department of Planning, Housing and Infrastructure — Low and Mid-Rise Housing Policy, summary of key provisions — dual occupancies permitted with consent in R2 zones state-wide. Non-discretionary standards in low and mid-rise housing areas: minimum lot size 450 m², minimum lot width 12 m, maximum floor space ratio 0.65:1, maximum height 9.5 m, one car space per dwelling, and subdivision in R1, R2 and R3 at a minimum 225 m² and 6 m width per lot. planning.nsw.gov.au/policy-and-legislation/housing/low-and-mid-rise-housing-policy/summary-of-key-provisions
- Wollongong City Council — Granny flats — describes secondary dwellings as self-contained, on the same property as a single existing home with at least 450 m² of land, no more than 60 m² in floor area, one per property, and states they cannot be subdivided from the main house and sold separately. Local council restatement of the state provisions. wollongong.nsw.gov.au/plan-and-build/building-and-renovating/common-residential-improvements/granny-flats
- NSW Department of Planning, Housing and Infrastructure — Low and Mid-Rise Housing Policy, frequently asked questions — Stage 1 commenced 1 July 2024 permitting dual occupancies and semi-detached homes in R2 zones across NSW; Stage 2 commenced 28 February 2025 within low and mid-rise housing areas. Defines low and mid-rise housing areas as residential zones within 800 metres walking distance of nominated town centres and stations. Lists excluded land. Explains that the complying development pathway under the Low-Rise Housing Diversity Code is available where dual occupancies are permitted with consent, and that non-discretionary standards apply only where more generous than the local plan. planning.nsw.gov.au/the-planning-system/housing/low-and-mid-rise-housing-policy/frequently-asked-questions
- NSW Department of Planning, Housing and Infrastructure — Secondary dwellings (granny flats), disaster recovery guidance — states that additional requirements apply on bushfire-prone land and that complying development is not available where land is classified as at risk of ember attack or exposure to flames from a fire front. planning.nsw.gov.au/the-planning-system/disaster-recovery/secondary-dwellings-granny-flats
Figures are as published by the sources above at their respective dates and are paraphrased summaries, not verbatim reproductions. Verify current pricing and rules directly with builders, lenders and planning authorities.