A duplex, in planning terms a dual occupancy, can be approved as complying development in NSW under Part 3B of the Codes SEPP, the Low Rise Housing Diversity Code. The site must be in a zone where dual occupancies are permitted with consent, must not be on excluded land such as a heritage item or certain flood control lots, must meet the Code’s minimum lot size and width, and the design must satisfy every numeric standard for height, FSR, setbacks, landscaping and parking. If all of that lines up, a private certifier can issue the CDC without a council merit assessment. If one thing does not, the project goes to a DA.
Key takeaways
- The Low Rise Housing Diversity Code allows one and two storey dual occupancies, manor houses and terraces as complying development where the LEP or Housing SEPP permits the use with consent in the zone.
- The Code has minimum lot size and width requirements for dual occupancies, and where the LEP sets a larger minimum lot size for dual occupancies that larger figure applies.
- Every standard is fixed: there is no Clause 4.6 or merit variation in a CDC, so a small shortfall means a DA.
- A design verification statement is required, confirming the design responds to the Low Rise Housing Diversity Design Guide.
- Since 1 July 2024 dual occupancies are permissible in all R2 zones across NSW, which has opened the CDC pathway on many Sydney lots where it was previously unavailable.
First gate: is a dual occupancy permitted with consent here
The Code only works where the use is already permitted with consent. Two sources of permissibility exist. The council’s LEP land use table for the zone, and since 1 July 2024 the Housing SEPP, which makes dual occupancies and semi-detached dwellings permissible in all R2 Low Density Residential zones across NSW with limited exclusions. The department’s Low and Mid-Rise Housing Policy FAQ confirms that the Code pathway is available where the state policy newly permits the use. In R3 and R1 zones dual occupancies were already permitted in most LEPs. In RU and E zones the Code generally does not apply, so a rural dual occupancy is a DA.
The section 10.7(2) planning certificate is the document to read first. It states the zone, whether the land is bushfire prone, flood affected, a heritage item or in a heritage conservation area, and whether complying development under each Code can be carried out on the land. Councils note on the certificate where the Code is excluded, which saves a lot of guesswork.
Second gate: excluded land
The Codes SEPP excludes some land from complying development entirely and some from particular Codes. For a duplex under the Low Rise Housing Diversity Code the common exclusions are:
- Heritage items and draft heritage items. Land in a heritage conservation area is also excluded for new dwellings under this Code in most cases.
- Certain flood control lots, unless the council has issued written confirmation or the development meets the flood related standards.
- Land with an environmentally sensitive overlay, some coastal land, and land identified in the LEP for particular protections.
- Land reserved for acquisition or with a road widening affectation.
Bushfire prone land is not automatically excluded, but the design must comply with Planning for Bush Fire Protection 2019 at a BAL the Code permits, which in the Hills, Hawkesbury and Wollondilly is often the deciding factor.
Third gate: lot size and width
The Code sets a minimum lot size for dual occupancies of 400 square metres, or the minimum lot size the LEP specifies for dual occupancies if that is larger. Many Sydney LEPs specify a minimum lot size for dual occupancies in R2 that is larger than 400 square metres, and where they do, that larger figure governs the CDC too. The Code also sets minimum lot widths at the building line, with a narrower minimum for attached dual occupancies and a wider one for detached. Read the current Code for the exact widths for your lot type, because the standard differs for corner lots and battle axe lots.
Two points that catch people: the lot width is measured at the building line, not the street boundary, and the LEP minimum lot size for dual occupancies is sometimes in a separate clause from the general clause 4.1 subdivision minimum, so check both.
The standards a certifier checks
Once the gates are passed, the certifier works through the numeric standards. The main ones for a dual occupancy under the Code are:
| Standard | What the Code controls | Where it usually bites in Sydney |
|---|---|---|
| Height | Maximum building height in metres and a two storey limit | Sloping lots in the Hills and on the Central Coast where the downhill side exceeds the limit |
| Floor space ratio | Maximum FSR set in bands by lot size | Owners wanting two four bedroom dwellings on a 500 square metre lot |
| Setbacks | Front setback tied to neighbours, side and rear setbacks that increase with height | Narrow lots in Cumberland, Fairfield and Canterbury-Bankstown |
| Landscaped area | Minimum landscaped area with minimum dimensions, plus front yard landscaping | Long driveways on rear access layouts |
| Private open space | Minimum area and dimension per dwelling with solar access | Up and down configurations |
| Parking | At least one off street space per dwelling, garage width limits facing the street | Frontages under 15 metres where two garages dominate the facade |
| Design | Design verification statement against the Design Guide | Standard builder plans not adapted to the site |
The numbers themselves are in the legislation and change from time to time. The Low Rise Housing Diversity Code page links to the current text and the Design Guide. We quote the standard directly from the Codes SEPP on the day we assess a site rather than from a summary sheet.
The design verification statement
Unlike the Housing Code for single houses, the Low Rise Housing Diversity Code requires a design verification statement. A qualified designer, as the Code defines that term, confirms the design has been prepared with regard to the Low Rise Housing Diversity Design Guide for complying development, which covers site analysis, orientation, open space, landscaping, privacy and streetscape. A certifier will not issue the CDC without it. Design practices such as Arqi prepare the design and statement together, and the design guides page has the current forms.
CDC or DA for a duplex: an honest comparison
| Question | CDC under the Code | DA to council |
|---|---|---|
| Who decides | Private certifier or council as certifier | Council under section 4.15 of the EP&A Act |
| Timeframe | Statutory target of 20 days once complete | Commonly several months |
| Variations | None, every standard must be met | DCP controls on merit, LEP standards through Clause 4.6 |
| Neighbour input | Notice only, no submissions | Notification and submissions considered |
| Design freedom | Within fixed standards plus Design Guide | Wider, subject to assessment |
| Subdivision | Available under the Code only where the LEP permits lots of that size | Assessed against clause 4.1 and any dual occupancy exception |
| Contributions | Section 7.11 or 7.12 still payable | Section 7.11 or 7.12 payable |
The Code suits a flat, regular lot above the minimum size with no heritage, flood or significant tree issues. A DA suits everything else, including a lot that is 20 square metres short or a scheme that needs an extra 300 millimetres of height. Our DA or CDC pathway advice matches the site to the route before money is spent on drawings.
A CDC is both the planning and construction approval, but BASIX under SEPP (Sustainable Buildings) 2022, stormwater to AS/NZS 3500.3:2021, any bushfire assessment and the section 138 Roads Act 1993 crossing approval all still sit around it, and section 7.11 or 7.12 contributions are still payable.
Frequently asked questions
Can a duplex be built as complying development in NSW?
Yes, under the Low Rise Housing Diversity Code in the Codes SEPP, provided dual occupancies are permitted with consent in the zone, the land is not excluded, the lot meets the minimum size and width, and the design meets every standard. A private certifier issues the certificate.
What is the minimum lot size for a duplex CDC?
The Code requires at least 400 square metres, or the larger minimum lot size the council LEP sets for dual occupancies. Many Sydney LEPs set a larger figure in R2, so check the LEP before assuming 400 square metres is enough.
Can I subdivide a duplex approved by CDC?
Only where the LEP already permits Torrens lots of that size. The Code includes subdivision of a dual occupancy as complying development but does not override the LEP minimum lot size. If the LEP does not allow it, strata subdivision is the usual alternative.
URBA assesses the site against the Code, tells you plainly whether it will pass, and coordinates the certifier, designer and engineers as part of our dual occupancy and duplex planning service across Sydney, the Central Coast and the Hunter. Send us the address and we will provide a fee proposal for a pathway check.