WA Granny Flat Rules 2026: Ancillary Dwelling Approvals

Updated 13 September 2026. Western Australian planning updates have clarified the WA granny flat rules 2026 under the amended Residential Design Codes (R-Codes), exempting compliant 70-square-metre ancillary dwellings from development approval across local government areas.

Key Changes Under the Amended State R-Codes

The revised State Planning Policy 7.3 removes long-standing administrative roadblocks for backyard builders in Perth and regional Western Australia. Under the deemed-to-comply criteria, property owners can construct an ancillary dwelling up to 70 square metres in plot ratio area on residential-coded land without submitting a formal Development Application (DA) to their local council, provided the design meets standard boundary setbacks and site open space requirements.

According to planning instruments published by the WA Department of Planning, Lands and Heritage and statutory provisions on Western Australian Legislation, the changes eliminate minimum lot size restrictions that previously barred properties smaller than 450 square metres from adding a second self-contained home.

The reforms also permanently enshrine the freedom to lease ancillary dwellings to unrelated members of the public, enabling homeowners to earn independent rental income while expanding affordable housing stock near transport corridors.

Building Licence and Engineering Still Mandatory

While planning exemption bypasses lengthy council committee meetings and neighbour consultation, it does not exempt your build from a certified Building Permit (Form BA1 or BA2). Before framing can start, an accredited private building surveyor or council certifier must approve your structural engineering, footings plan, and bushfire risk rating.

In sandy coastal soil across suburban Perth, soil classification testing determines whether a standard concrete slab or engineered steel piers offer the most cost-effective foundation. If your property is mapped within a Bushfire Prone Area, your building certifier will also enforce Bushfire Attack Level (BAL) construction materials, which can add substantial costs for toughened glazing and non-combustible cladding. Review how national building approval stages align in our guide to granny flat regulations Australia by state.

Siting and Service Connection Planning

The 70-square-metre allowance in Western Australia is one of the most generous in the country, allowing comfortable two-bedroom floor plans with full kitchens and dedicated laundry facilities. However, you must maintain designated open garden space and ensure private outdoor living areas do not overlook neighbouring fences.

To calculate site preparation, earthworks, and sub-metered utility runs, compare typical trade prices in our national report on granny flat costs in Australia. You can estimate total project costs using our interactive granny flat cost calculator, or connect with licensed local builders via request builder quotes. All major planning updates are archived under Granny Flat Guide News.