Dual Occupancy: Build Two Homes on One Block

Dual occupancy — building two dwellings on a single residential lot — is one of the most effective ways to maximise the value of your land. Whether you want to live in one and rent the other, house extended family, or sell one off, understanding the rules is essential before you invest in plans and approvals.

What Is Dual Occupancy?

A dual occupancy (also called "duplex" or "dual occ") means two separate dwellings on one lot. This can take several forms:

• Attached dual occupancy: Two dwellings sharing a common wall (like a duplex or semi-detached pair)
• Detached dual occupancy: Two separate buildings on the same lot, typically one at the front and one at the rear
• Dual occupancy with subdivision: The lot is divided into two Torrens titles, each with its own dwelling — creating two fully independent properties

Note: a dual occupancy is different from a granny flat/secondary dwelling. A granny flat is subordinate to the main house and generally cannot be separately titled. A dual occupancy creates two equal dwellings.

Lot Size Requirements by State

Minimum lot sizes for dual occupancy vary significantly by state and by the specific zone within each council area:

NSW

• Minimum lot size is set by the council's LEP — typically 600–800sqm for detached dual occ in R2 (Low Density Residential) zones
• Some councils allow attached dual occ on lots as small as 450–500sqm
• R3 (Medium Density) zones often have lower thresholds
• CDC pathway available if all standards in the Codes SEPP are met (including lot width, setbacks, landscaping)
• If subdividing, each resulting lot must meet the council's minimum lot size requirement

Victoria

• The General Residential Zone (GRZ) allows two dwellings on a lot (no permit required for the use, but a planning permit is needed for the building)
• Minimum lot size varies — many councils set it at 500–650sqm
• Must comply with ResCode (Clauses 54 and 55 of the planning scheme)
• The Neighbourhood Residential Zone (NRZ) may restrict dual occupancy in some areas — check your zone
• Garden area requirement: a minimum percentage of the lot (typically 25–35%) must be permeable garden area

Queensland

• Rules vary by local government, but dual occupancy is generally permitted in Low-Medium Density Residential zones
• Typical minimum lot size: 600–800sqm
• Often code-assessable (no public notification required)
• Subdivision rules are set by the local council's planning scheme

South Australia

• Under the Planning and Design Code, dual occupancy is assessed against the General Neighbourhood Zone or Suburban Neighbourhood Zone criteria
• Minimum lot sizes vary by zone and subzone — commonly 450–700sqm
• "Deemed to satisfy" pathway available for compliant designs

Western Australia

• Governed by the Residential Design Codes (R-Codes)
• The R-Code assigned to your lot determines minimum lot sizes for grouped dwellings — e.g. R20 allows one dwelling per 500sqm, R30 allows one per 300sqm
• Dual occupancy is generally straightforward in zones R25 and above

Attached vs Detached: Pros and Cons

Factor	Attached	Detached
Lot size required	Smaller (450–600sqm)	Larger (600–800sqm+)
Construction cost	Lower (shared wall)	Higher (two separate structures)
Privacy	Less (shared wall)	More (separate buildings)
Subdivision	Easier (common wall on boundary)	More complex (driveway access, services)
Market appeal	Good for owner-occupiers	Good for investors and families
Design flexibility	More constrained	More flexible

Cost Range for Dual Occupancy (2026)

Total project costs depend heavily on location, design, and whether you subdivide:

• Demolition of existing home: $20,000–$40,000
• Construction of two dwellings (attached, mid-spec): $700,000–$1,200,000 total
• Construction of two dwellings (detached, mid-spec): $800,000–$1,400,000 total
• Council fees and contributions: $15,000–$60,000
• Professional fees (surveyor, planner, engineer): $15,000–$30,000
• Subdivision costs (if applicable): $15,000–$40,000 (survey, council fees, linen plan)
• Total project range: $800,000–$1,800,000+

The Subdivision Option

If your council allows it and the lot is large enough, you can subdivide after (or concurrently with) construction to create two separate Torrens titles. This is powerful because:

• Each dwelling becomes an independent, sellable property
• Separate titles generally achieve higher sale prices than strata-titled units
• Each buyer can get a standard home loan (not an investor loan for a unit)

The subdivision process involves a surveyor preparing a plan of subdivision, council approval, and registration with your state's land titles office. Budget 3–6 months and $15,000–$40,000 for the process.

Key Considerations

• Driveway access: Both dwellings need legal and practical access to the street. A shared driveway with an easement may be required for rear dwellings.
• Parking: Most councils require 1–2 car spaces per dwelling
• Private open space: Each dwelling must have usable private outdoor space — typically 24–40sqm minimum
• Overlooking and overshadowing: Your design must demonstrate that neither dwelling unreasonably impacts neighbours or the other dwelling
• Infrastructure contributions: Councils may charge developer contributions for the additional dwelling
• Financing: Construction loans for dual occupancy are more complex — some lenders treat it as a development loan with stricter criteria

Is Dual Occupancy Right for Your Block?

The first question is always: does your lot meet the minimum size and zoning requirements? Check your council's planning controls, or run a quick check on AusBuildCircle.com to see whether dual occupancy is feasible on your block.