Western Australia has proposed raising the granny flat (ancillary dwelling) limit from 70 m2 to 90 m2. The draft Residential Design Codes released by the Western Australian Planning Commission on 24 October 2026 would increase the maximum internal floor area for ancillary dwellings to 90 m2 and drop the extra parking bay in Perth and Peel. It is a draft: until it is finalised, the 70 m2 limit still applies.*
What applies today
- A granny flat that meets the deemed-to-comply provisions of the R-Codes, up to 70 m2, does not need development approval, on a lot of any size (since April 2024).
- A building permit is still required.
- Larger or non-complying designs go through development approval with your local government.
What the draft proposes
- 90 m2: the maximum internal floor area for all ancillary dwellings rises from 70 m2 to 90 m2.
- Parking: no additional parking bay for an ancillary dwelling, except outside the Perth and Peel regions.
- Larger again: local governments could allow ancillary dwellings over 90 m2 through a local planning policy, without separate WAPC approval.
- Incidental: the design principles add that the ancillary dwelling must remain incidental to the main house.
- Small dwellings stay at 70 m2: the separate small dwelling limit is not changing.
Key dates
Consultation opened on 24 October 2026 and submissions close at 5.00pm AWST on Friday 26 February 2027. The final codes then go to the WAPC. If you are planning a granny flat now, design to 70 m2 for the exempt pathway, or talk to your local government about the timing.
What 90 m2 would allow
At 70 m2 most layouts are a compact two bedroom or a generous one bedroom. At 90 m2 a two bedroom home with a separate living area, a full bathroom, a laundry and storage fits comfortably, which suits a parent, an adult child or a long-term tenant.
How a modular granny flat fits
As the manufacturer, EcoPrestige is responsible for every module: built and inspected in an offsite factory to Australian engineering and QA, then delivered to site. The module sizes are set against the floor area limit and your block before anything is drawn, so the home stays inside the rule that applies on the day you lodge.
Start with Step 1 of our Domestic Program, which checks the site, the planning position, truck and crane access, and cost before you commit. More for WA: modular homes in regional WA | granny flats Bunbury | who can design a granny flat in WA.
Frequently asked questions
What is the granny flat size limit in WA right now?
70 m2 for a granny flat that meets the deemed-to-comply provisions of the R-Codes and so needs no development approval. The 90 m2 limit is a draft proposal released for consultation on 24 October 2026 and is not yet in force.
When could the 90 m2 limit start?
Submissions close on 26 February 2027. The final codes then go to the Western Australian Planning Commission, so the start date is not yet set.
Will a 90 m2 granny flat need a car bay?
The draft proposes no additional parking bay for an ancillary dwelling in Perth and Peel. Outside those regions, parking would still apply.
Do I need a building permit for a granny flat in WA?
Yes. A building permit is required, even where no development approval is needed.
Sources
- Western Australian Planning Commission, Draft Residential Design Codes, Table of Changes and Information Sheet 3: Simpler rules for lower density development, released for consultation 24 October 2026; submissions close 5.00pm AWST Friday 26 February 2027 (haveyoursay.dplh.wa.gov.au/r-codes-review).
- WA Government media statement, 29 January 2024: compliant granny flats up to 70 m2 no longer need development approval on lots of any size, operational from mid-April 2024 (wa.gov.au).
This is general information, not legal advice. The draft is not law until it is finalised. Your local government and building surveyor confirm the rules for your lot.
Send your address and a photo of the site to prebuilt@ecoprestige.com.au. Send your enquiry first so you’re fully informed.
*Rules vary by state. Design and building work is carried out by the licensed or registered practitioner your state requires.