WA Granny Flat Rules Have Change-Here's What Every Homeowner Needs to Know

Since April 2024, Western Australia's new planning rules have made it significantly easier and faster to build a granny flat on your property. Here's a plain English breakdown of what changed and what it means for you.

Western Australia has long grappled with one of the tightest rental markets in the country. Perth consistently records the lowest vacancy rate of any Australian state capital, and the pressure on housing stock has pushed both renters and homeowners to look for creative solutions.

One of the most practical answers? The humble granny flat. And as of mid-April 2024, the WA State Government has made building one considerably easier, faster, and more accessible than ever before.

Whether you're thinking about housing an ageing parent, bringing in some rental income, or simply making better use of your backyard, here's everything you need to know about the new rules.

Why did the rules change?

The WA Government announced relaxed amendments to the Residential Design Codes (R-Codes) in January 2024, with the changes taking effect in April that year. The driving force was straightforward: not enough homes.

"Western Australia is in the midst of a housing crisis and there is not enough stock on the market or available to rent to meet rising demand."

— Tanya Steinbeck, CEO, Urban Development Institute of Australia (WA)

The previous planning framework imposed several barriers that discouraged homeowners from building granny flats, most notably minimum lot size requirements that shut out a large proportion of Perth's suburban blocks. The new rules are designed to remove as much of that red tape as possible.

What's actually changed?

The key rules that still apply

While the approval pathway has been streamlined considerably, a granny flat must still meet certain conditions to qualify for the simplified process. Think of these as the non-negotiables:

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  Maximum size of 70m² — The floor area of the granny flat must not exceed 70 square metres. Most two-bedroom designs fit comfortably within this limit, with room for a bathroom, kitchen and open-plan living.
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  Setback requirements — The structure must be positioned at least 1 metre from property boundaries, and must comply with the applicable setback rules in the R-Codes based on boundary wall length and height. Check Tables 2A and 2B of the R-Codes for specifics.
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  Secondary dwelling only — A granny flat is classified as an ancillary (secondary) building. It cannot be the first or only structure on a vacant lot — there must already be a primary dwelling on the property.
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  Building permit still required — While planning approval is no longer needed, you must still obtain a building permit from your local council or a private building surveyor. The good news: this typically takes no more than 10 business days.
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  National Construction Code compliance — All builds must meet the NCC's safety and quality standards, regardless of size or location.
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  Parking (conditional) — If your property is within 800m of a train station or 250m of a high frequency bus route, no additional car bay is required. Beyond those distances, one car space at the granny flat is still needed.
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  One per lot — Only one granny flat is permitted per lot, unless you have specific permission under the local planning scheme.

How much faster is the process now?

The streamlining has had an immediate effect on demand. Major WA builder Summit Homes reported a nearly 125% rise in granny flat enquiries following the announcement reflecting just how many homeowners had previously been put off by the red tape.

Who can I rent my granny flat to?

Under the previous rules, many councils restricted granny flat occupancy to family members of the main dwelling's residents. That restriction has now been lifted in most cases across Perth and regional WA meaning you can rent your granny flat to anyone you choose, including via platforms like Airbnb.

That said, some councils (such as the City of Stirling) still require written consent before renting to non family members. Always check with your specific local government before listing or renting to confirm any additional local conditions that may apply.

What does a granny flat cost to build in WA?

Costs vary depending on size, design, materials and builder. The average cost to build a granny flat in WA sits around $120,000, though this can be significantly lower for simpler designs or kit/modular builds, and higher for more custom or premium finishes.

The removal of the planning approval stage has also reduced design and professional fees for most projects, with some all-in design-and-approval services starting from around $7,000, compared to $15,000 to $30,000 or more under the previous system.

Does this apply to my property?

The simplified pathway applies to most metropolitan Perth properties, including suburbs across Joondalup, Wanneroo, Midland, Rockingham, Mandurah, Baldivis and beyond. Your property needs to be zoned Residential at R20 or above under the relevant local planning scheme.

If you're unsure about your lot's zoning or whether the new rules apply to your specific block, the best first step is to check with your local council's planning department or visit the Western Australian Planning Commission (WAPC) website for up-to-date guidance and fact sheets.

The bottom line

Western Australia's granny flat reforms are a genuine win for homeowners. The removal of minimum lot sizes and planning approval requirements, combined with a building permit process measured in days rather than months has opened the door to a practical, affordable way to increase housing supply and generate additional income from existing properties.

If you've been sitting on the idea of a granny flat, now really is the easiest time to make it happen. Just make sure your build stays under 70m², meets the R-Code setback requirements, and get your building permit sorted before breaking ground.