Granny Flat Rules by State: What You Can Build in 2026

Granny flats — also called secondary dwellings, ancillary dwellings, or dependent person's units — are one of the most popular ways to add value and functionality to a residential property in Australia. But the rules governing what you can build, how big it can be, and what approvals you need vary significantly from state to state.

New South Wales

NSW has the most streamlined granny flat framework in the country, thanks to the State Environmental Planning Policy (Affordable Rental Housing) 2009 — commonly called the "Granny Flat SEPP."

Key rules:

• Maximum size: 60 square metres of internal floor area
• Minimum lot size: 450 square metres
• Approval pathway: Can be approved as Complying Development (CDC) by a private certifier — no DA required if all standards are met
• One per lot: Only one secondary dwelling per lot
• No separate subdivision: Cannot be strata-titled or Torrens-titled separately from the main dwelling
• Can be rented: Unlike some states, NSW allows granny flats to be rented to non-family members
• Setbacks: Minimum 0.9m from side and rear boundaries
• Height: Maximum 3.8m (single storey)

The 60sqm limit includes internal floor area only — it does not include covered verandahs, carports, or garages (up to a point).

Victoria

VIC calls them "secondary dwellings" or "dependent person's units" (DPU), and the rules are significantly more restrictive than NSW.

Key rules:

• Dependent Person's Unit (DPU): Can be approved without a planning permit in many zones, but must be for a "dependent person" (family member) — not for general rental
• Secondary dwelling (for rental): Requires a planning permit and must comply with Clause 54/55 (ResCode)
• Maximum size for DPU: Generally limited to one bedroom, no more than about 50–60sqm depending on council
• Recent reforms: The Victorian Government has been progressively making it easier to build secondary dwellings, particularly in areas well-served by public transport. Check with your council for the latest position
• No separate title: Cannot be subdivided separately

Queensland

QLD allows "secondary dwellings" under its planning framework, but rules vary by local government area.

Key rules:

• Maximum size: Typically 80 square metres (some councils allow up to 90sqm)
• Minimum lot size: Varies by council, typically 600–800 square metres
• Approval pathway: Often "code assessable" rather than requiring full impact assessment — faster than a traditional DA
• Can be rented: Yes, to anyone
• Height: Generally 1 storey, max height varies by zone
• Flood overlays: QLD has extensive flood mapping — check your lot

South Australia

Under the new Planning and Design Code, SA has simplified secondary dwelling rules.

Key rules:

• Maximum size: Generally 60 square metres
• Minimum lot size: Varies by zone, typically 450–600sqm
• Approval pathway: May qualify as "deemed to satisfy" (fast-track) if all criteria met
• Can be rented: Yes
• Self-contained: Must include kitchen, bathroom, and sleeping areas

Western Australia

WA calls them "ancillary dwellings" and has been gradually liberalising the rules.

Key rules:

• Maximum size: 70 square metres
• Minimum lot size: Varies by R-Code zoning (e.g. R20 typically requires 450sqm+)
• Approval pathway: May be approved as "deemed to comply" under the R-Codes
• Occupancy restrictions: Some local governments still require the occupant to be a family member — check your local planning scheme
• Must be ancillary: The granny flat must be subordinate to the main dwelling

ACT and Tasmania

ACT: Secondary residences (called "supportive housing" or "secondary residence") are permitted in certain zones. Maximum size generally 90sqm. Lease variation may be required.

Tasmania: "Ancillary dwellings" permitted in General Residential zones. Maximum 60sqm floor area. Planning permit usually required.

Cost to Build a Granny Flat

Costs vary depending on whether you build custom, use a kit, or go with a prefab/modular solution:

• Kit or prefab (basic): $80,000–$130,000 installed
• Custom build (mid-range): $130,000–$200,000
• High-end custom: $200,000–$300,000+

These figures include site preparation, slab, construction, and connection to services. They do not include any required driveway upgrades or landscaping.

Common Mistakes to Avoid

• Not checking zoning first: Not all residential zones allow secondary dwellings. Verify before you spend money on plans.
• Forgetting about services: Water, sewer, and electricity connections can cost $10,000–$30,000 depending on distance from mains.
• Ignoring stormwater: Adding impervious surface (the granny flat roof and slab) increases stormwater runoff. Most councils require an on-site detention system.
• Assuming you can subdivide later: In most states, granny flats cannot be separately titled. If your goal is subdivision, look at dual occupancy instead.
• Underestimating council fees: Development contributions can add $5,000–$20,000 to your project.

Is a Granny Flat Right for You?

Granny flats make financial sense when you need rental income, multigenerational living space, or a home office. Check your specific council's rules before committing — or use the feasibility tool on AusBuildCircle.com to get a quick assessment of what is possible on your block.