Building a duplex in Blacktown: LEP 2015 and DCP controls that matter

A duplex in Blacktown is decided by a short list of controls: the zone and minimum lot size in Blacktown LEP 2015, the frontage, setback, landscaping, parking and private open space controls in Blacktown DCP 2015, and council’s stormwater and flood requirements. If your lot passes the LEP lot size test and the DCP frontage test, the rest is design. If it fails either, no amount of good design fixes it, unless the lot sits inside one of the low and mid-rise housing catchments around a station, where State standards now sit over the local ones.

Which Blacktown controls apply to your lot

Blacktown has two planning systems running side by side.

The s10.7(2) certificate names the instrument. This post deals with the established suburbs under the LEP and DCP; the growth precincts have their own lot sizes and estate covenants, and the Department’s North West Growth Area page is the place to start for those.

Blacktown LEP 2015: the two lot size tests

Blacktown LEP 2015 permits dual occupancies in the R2 Low Density Residential, R3 Medium Density Residential and R4 High Density Residential zones. Since 1 July 2024, Stage 1 of the State’s Low and Mid-Rise Housing policy has also made dual occupancies and semi-detached dwellings permissible in every R2 zone in NSW, so permissibility is rarely the issue in Blacktown. The numbers are.

1. Minimum lot size to build the duplex. The LEP sets a minimum lot area for a dual occupancy in the R2 zone, with different treatment in places for attached and detached forms. Many post-war lots in Seven Hills, Lalor Park, Blacktown and Doonside are in the 550 to 700 square metre range and clear the figure; many 1990s lots in Glenwood, Stanhope Gardens and Kellyville Ridge do not. Check the current clause and the lot size map rather than relying on a neighbour’s approval.
2. Minimum lot size to subdivide the duplex. The LEP contains a separate clause that allows Torrens subdivision of a dual occupancy where each resulting lot meets a specified minimum area. That figure is what decides whether you end up with two Torrens titles or a strata plan, and it is worth confirming before a feasibility assumes two saleable Torrens lots. Our subdivision planning service handles the subdivision DA alongside the duplex.

Since 28 February 2025, Stage 2 of the Low and Mid-Rise Housing policy has applied within 800 metres walking distance of nominated stations and centres in the Six Cities Region. Blacktown, Seven Hills, Mount Druitt and other centres along the Western Line are in scope. Inside those catchments a dual occupancy can rely on State non-refusal standards for lot size, height, FSR and setbacks that sit over Blacktown LEP 2015, and terraces, townhouses and manor houses become permissible in R2. The catchment is measured on foot and excludes heritage conservation areas and flood and bushfire affected land, so a site-specific check is needed.

Blacktown DCP 2015: the design controls that decide the DA

Blacktown DCP 2015 sets out its residential controls in the part dealing with development in the residential zones. On duplex DAs across the established suburbs, these are the controls that generate most of the requests for information and the refusals we see:

Frontage and garage width

The DCP sets a minimum frontage for a dual occupancy, with a larger figure for a detached pair and a rule for battle-axe lots. It also limits garage width to a proportion of the facade and requires the garage to sit at or behind the front wall. Two double garages across a standard 15 to 18 metre frontage almost never comply, which is why most compliant Blacktown duplexes use single garages with a tandem or open space in front.

Setbacks and building envelope

Front setbacks follow the street pattern; side and rear setbacks step up with wall height.

Landscaped area and private open space

The DCP requires a minimum landscaped area as a proportion of the site, with a portion in the front setback, and a minimum private open space per dwelling with a minimum dimension directly off a living room. The second driveway is what eats the landscaping. Battle-axe designs with a shared driveway usually do better here than side-by-side pairs.

Parking and access

Generally one covered space per dwelling plus a second space, designed to AS 2890.1:2004 for widths and gradients, with a limit on the number and width of driveway crossings per frontage. Corner lots in Blacktown can often take one driveway from each street, which solves both the crossing count and the garage dominance problem.

Where a control cannot be met, the Statement of Environmental Effects should say so and explain why the DCP objective is still met. An honest variation does better than a silent one.

Stormwater and flooding: the technical items that hold up Blacktown DAs

Blacktown sits in the Eastern Creek, South Creek, Breakfast Creek and Toongabbie Creek catchments, and council’s engineering requirements are detailed. On a duplex DA expect:

• On-site detention (OSD) on most sites, designed to council’s engineering guide, with a stormwater plan that shows the tank, the outlet and the legal point of discharge.
• A flood assessment where the lot is within the flood planning area, common along Breakfast Creek in Marayong and Blacktown, Eastern Creek through Rooty Hill and Doonside, and Bells Creek through Kings Langley. Flood-affected lots also lose the Low Rise Housing Diversity Code complying development option.
• Rear lot drainage. A lot that falls away from the street needs an interallotment drainage easement over the neighbour or a charged system.

A civil engineer such as Contrive Consultants prepares the stormwater and OSD design alongside the SEE.

DA or complying development in Blacktown?

The Low Rise Housing Diversity Code lets a private certifier approve a dual occupancy as complying development where the lot meets the code’s size and width requirements and none of the exclusions (flood control lot, bushfire prone land, heritage, some environmentally sensitive land) apply. The trade-off is that the code’s standards are fixed, so if your lot is marginal on width, setback or landscaping, or if the LEP subdivision rules are more generous than the code, the council DA is the better path. The Blacktown City Council website publishes the LEP, the DCP and the engineering guide, and our DA or CDC pathway advice compares the two routes for a specific address.

URBA prepares Statements of Environmental Effects, pathway advice and subdivision planning for duplexes across Blacktown every week, and we coordinate the stormwater and flood inputs council expects. See our Blacktown town planning page for how we work with the council, or request a fee proposal for your lot.