Can I build a duplex on my property? NSW rules explained

You may be able to build a duplex on your property in NSW if the land permits dual occupancy and the design meets the rules for your approval pathway. In eligible low and mid-rise housing areas the state standards include a 450 m² lot and 12 m width at the front building line. Those figures do not make every block eligible or replace the separate tests for complying development. NSW Planning explains where the standards apply.

The first decision is what your particular site can support. We approach duplex design and construction in Sydney by reading the site controls before drawing the two homes. The aim is a pair with its own light, privacy and outdoor space on each side.

Planning information checked on 19 October 2026.

What changed under the NSW housing reforms?

The reforms widened where dual occupancies can be considered. They did not give every owner permission to start building.

From 1 July 2024 dual occupancies and semi-detached homes became permitted with consent in R2 low-density residential zones across NSW, subject to exclusions. From 28 February 2025 further controls applied in eligible low and mid-rise housing areas. NSW Planning sets out the two stages.

A dual occupancy is two dwellings on one lot. They can be attached or detached. A granny flat is a secondary dwelling and follows different rules. If your intention is to create two separately saleable homes, start with that distinction. See NSW Planning's housing definitions.

What is the minimum lot size for a duplex in NSW?

There is no single minimum lot size that answers every NSW duplex proposal. Establish which of these situations applies before using a number from a property listing.

A DA in an eligible low and mid-rise housing area

For dual occupancies in R1, R2, R3 or R4 zones within an eligible area, section 168 of the Housing SEPP sets these non-discretionary standards:

1. A minimum lot area of 450 m².
2. A minimum lot width of 12 m at the front building line.
3. A maximum floor space ratio of 0.65:1.
4. A maximum building height of 9.5 m.
5. At least one car parking space per dwelling where no applicable planning instrument or development control plan specifies a maximum number of spaces per dwelling.

Read the current Housing SEPP provisions.

Non-discretionary means council cannot refuse an application on that particular standard when the proposal meets it. Other relevant assessment matters remain. A more generous local standard can still apply. These are not five boxes that guarantee consent. NSW Planning explains how state and local controls work together.

A DA outside those areas

Your council's Local Environmental Plan (LEP) and Development Control Plan (DCP) remain central to the assessment. R2 permissibility does not automatically give the site the 450 m² and 12 m standards.

Council variation is real. Parramatta Council describes its local dual occupancy requirements as a minimum 600 m² lot with 15 m frontage to a public road unless the site is within a low and mid-rise housing area. That is a local example rather than a Sydney-wide rule. Read Parramatta's dual occupancy guidance.

A duplex using complying development

The Low Rise Housing Diversity Code has its own lot and design tests. For the usual side-by-side arrangement, clause 3B.8 requires the greater of 400 m² and the applicable instrument's minimum dual occupancy lot area. It expressly excludes the Housing SEPP's Chapter 6 dual occupancy non-discretionary standards from that comparison.

The parent lot must generally be at least 15 m wide at the building line. The 12 m alternative applies where parking is accessed only from a secondary road, parallel road or lane. A 12 m street frontage with two driveways to the primary road does not satisfy that alternative. See the current Low Rise Housing Diversity Code.

How do I know whether my block is in an eligible area?

An eligible low and mid-rise housing area is based on walking distance to nominated centres or stations. Being near any station is not enough.

The definition uses 800 m walking distance from a mapped town centre or a nominated railway, metro or light rail station entrance. For a nominated light rail stop without an entrance it uses the platform. It also covers a site area that contains qualifying land. The walk must follow a route pedestrians can safely use. Read the definition and exclusions in the Housing SEPP.

Start with the NSW Planning Portal Spatial Viewer. Check the zone, relevant maps and property constraints. Use the indicative low and mid-rise map as a starting point then establish the actual walking route and legislative coverage.

Check exclusions before spending time on a floor plan. They include bushfire-prone land, specified flood-affected land, heritage items and certain coastal areas. Aircraft noise, pipeline buffers and Transport Oriented Development areas can also matter. The current legislation includes additional mapped exclusion areas. These tests apply to the individual site, not simply its suburb. NSW Planning's exclusions guide explains the main categories.

A heritage item and a heritage conservation area are different designations. Do not assume that every property in a conservation area is excluded from the low and mid-rise policy. Equally, do not assume that this makes it eligible for CDC. Check each pathway's heritage controls. NSW Planning lists heritage conservation areas among the code exclusions.

Can I use a CDC for a duplex in NSW?

Possibly. A complying development certificate combines planning and construction approval for a proposal that meets the applicable requirements. A council or registered certifier assesses it against those standards. A development application is the route for a proposal requiring merit assessment. Our guide to DA or CDC: choosing the right approval path explains the broader distinction.

Current NSW Planning guidance says the code can be used where an environmental planning instrument permits the development with consent. That can include places where the housing reforms newly permit it. An older statement that only the council's LEP can provide that permission is no longer a complete guide. The proposal still has to meet the code. See NSW Planning's explanation of the relationship between the reforms and CDC.

For a side-by-side duplex under Part 3B, the early checks extend beyond area and width:

1. The code applies in RU5, R1, R2 and R3 zones. The lot needs lawful access to a public road. R4 is not on that list.
2. The maximum building height is 8.5 m above existing ground level. This differs from the 9.5 m non-discretionary DA standard.
3. For a parent lot from 400 m² to 2,000 m², maximum gross floor area for all buildings is 25% of the lot area plus 300 m². Above 2,000 m² the cap is 800 m².
4. Each dwelling needs at least one off-street parking space. Setbacks, landscaping, private open space and privacy controls also apply.
5. Battle-axe lots and unsewered land are excluded from this code. Building over a registered easement is excluded too. Each dwelling must face a public road with limited arrangements for corner or parallel road lots.

These are initial checks for a duplex with no dwelling above the other. Stacked dwellings have a different part of the code. Read Part 3B before selecting the pathway.

Have the certifier review the proposed layout and constraints early. Passing a lot-size check is only the beginning of CDC assessment.

Can I subdivide a duplex into Torrens titles?

Building two dwellings and creating two separate lots are separate planning questions. Check both at the start if you intend to sell one home independently.

The Housing SEPP provides a subdivision route for eligible dual occupancies in low and mid-rise housing areas in R1, R2 and R3 zones. Section 169 requires each resulting lot to:

1. Contain no more than one dwelling.
2. Have at least 6 m width at the front building line.
3. Have lawful access and frontage to a public road.
4. Have an area of at least 225 m².
5. Be a lot other than a battle-axe lot.

There is also a date condition. The dual occupancy must have received development consent on or after 28 February 2025 or result from an application made on or after that date for both subdivision and construction of the dual occupancy. Section 169 does not apply to strata subdivision. Read the full subdivision provision.

Do not transfer those figures to a CDC subdivision without checking the separate code provisions. Ask the planner, registered surveyor and certifier to test the intended boundary, road access and servicing arrangement together. A dwelling approval alone does not settle the title outcome.

What should I check before commissioning a duplex design?

Gather the property information first then test a simple layout against the controls. This makes the design brief more useful than starting with a preferred floor plan and trying to fit the land around it.

1. Obtain a current planning certificate and check the zoning, overlays and applicable instruments with your planner.
2. Have a surveyor establish the boundaries, levels and width at the building line. A width measured at the front fence may not describe a tapered block where the building will sit.
3. Review the title and easements alongside sewer and stormwater information. Mark the land that is actually available for building.
4. Test access, parking and the intended subdivision before resolving room sizes. Include landscape and outdoor space in the first layout.
5. Assess how both homes receive daylight and protect privacy. Consider the shared wall, window placement and the proportion of the pair from the street.

This sequence draws on the NSW Planning code requirements and our approach to designing two homes on one site. A planner or certifier needs to assess the particular property before you rely on an approval route.

How does SHORE approach duplex sites?

We bring design and construction together so the planning envelope and the quality of each home are considered from the start.

SUTHERLAND in Mascot is a dual occupancy with DA approval. BELLA in Clovelly is a dual occupancy under construction. Their different stages matter when considering the work involved between an approved design and finished homes.

We designed and built SOL in Bondi Beach, completed in 2025. It set a Bondi Beach suburb record for a duplex. Its curved forms and natural finishes show the architectural care that two homes can share while retaining their own character.

Each project begins with its own site and brief. Approval on your land rests on its own controls.

Start with your block

Tell us where the property is and how you want to use the two homes. Bring any survey or existing plans to the first conversation. We can discuss the site and the design brief before the project moves further.

Discuss your duplex with SHORE.