If you own property in Bunbury or the South West, there has never been a better time to consider building a granny flat. Western Australia’s residential planning rules changed significantly in April 2024, and the flow-on effects are still being felt across regional centres like Bunbury — where housing demand remains high and land supply is tight.
Whether you’re looking to house ageing parents, generate rental income, or add long-term value to your property, understanding the current rules before you start is essential. Here’s a straightforward guide to what applies in WA in 2026.
What Changed in WA’s Granny Flat Rules?
The big shift came on 10 April 2024, when the Western Australian Government amended the Residential Design Codes (R-Codes) to make it significantly easier for homeowners to build ancillary dwellings — officially referred to as granny flats.
The key changes were:
The minimum lot size requirement was scrapped. Previously, you needed a residential lot of at least 350 square metres to build a granny flat. That requirement no longer exists. If your property is zoned residential and meets the relevant R-Codes, you can now build a granny flat regardless of lot size.
No planning approval required — for most builds. As long as your ancillary dwelling is 70 square metres or under and complies with your local council’s setback and design requirements, you do not need to lodge a planning application. This alone has dramatically reduced red tape for South West WA homeowners.
Design compatibility rules removed. Granny flats no longer need to visually match the main dwelling on your property. This gives builders and homeowners much more flexibility in materials, roofline, and style — particularly useful in coastal areas like Bunbury where a more contemporary structure might make more sense than replicating an older brick home.
Parking requirements relaxed in some areas. Properties within close proximity to public transport are no longer required to provide a dedicated car bay for the ancillary dwelling.
What Approvals Do You Still Need?
Removing the planning approval requirement doesn’t mean building without oversight. Here’s what still applies in 2026:
Building permit — mandatory for all granny flat construction. This is issued by your local council or a licensed private building certifier. The good news is that under the revised rules, straightforward building permit applications should be processed within 10 business days. The permit ensures your structure meets the Building Code of Australia’s structural, safety, and energy efficiency requirements.
Local council setback requirements. Your granny flat must maintain appropriate distances from property boundaries, neighbouring structures, and the primary dwelling. These setbacks are set by your local government — in Bunbury’s case, that’s the City of Bunbury — and they can vary by zoning. Always check with council or your builder before committing to a floor plan.
Plot ratio limits. The total floor area of all structures on your property (including the granny flat) must still comply with the allowable plot ratio under your zoning classification.
Utility connections. You will need to connect the granny flat to water, sewer, and electricity. In Bunbury, most residential lots have good access to reticulated services, but connection costs can range from $5,000 to $15,000 depending on the distance from the main dwelling and the condition of existing infrastructure.
What Does It Cost to Build a Granny Flat in South West WA?
Costs vary considerably depending on the size, finish, site conditions, and whether you use a transportable or site-built structure. As a general guide for the South West WA region in 2026:
- Basic single-room studio (up to 40m²): $80,000–$120,000
- One-bedroom ancillary dwelling (50–60m²): $120,000–$175,000
- Two-bedroom dwelling (close to the 70m² cap): $170,000–$230,000+
Keep in mind that site-specific costs — such as sloping blocks, soil conditions, tree removal, or stormwater management — can add to the base build price. The South West’s coastal soils, particularly in lower-lying areas of Bunbury near the estuary, can sometimes require engineered footings, which adds cost but is non-negotiable for a structurally sound build.
Permit and approval fees are generally under $10,000 for a straightforward project.
Why Bunbury Makes Sense for a Granny Flat Investment
Bunbury’s property market has been one of the strongest performers in regional Australia. The city recorded 20.7% growth in dwelling values over the past year — the highest annual growth rate of any major regional market in the country — and with median house prices now above $780,000, rental demand in the area remains robust.
A well-built granny flat in Bunbury can generate between $350 and $500 per week in rental income depending on size, location, and finish level. With vacancy rates still low across the South West, homeowners who act now are well positioned to benefit from both rental returns and capital growth.
There’s also a practical dimension. The South West’s ageing population means many families are looking for ways to keep multiple generations on the one property — close enough to support one another, but with the privacy and independence a separate dwelling provides.
Climate Considerations for South West WA Builds
Building in Bunbury and the South West WA region means accounting for a Mediterranean-style climate with warm, dry summers and mild, wet winters. A few practical considerations for your granny flat build:
Insulation and orientation matter more than many people realise. A north-facing structure with appropriate eaves will stay cooler in summer and warmer in winter without heavy reliance on heating and cooling.
Bushfire Attack Level (BAL) ratings may apply if your property is on the urban fringe or near bushland. Even within Bunbury’s urban boundary, pockets of vegetation can trigger BAL requirements that affect materials and construction methods.
Stormwater management needs careful thought, particularly in low-lying areas. The City of Bunbury has specific requirements around how additional impervious surfaces (like a granny flat footprint) are managed on your block.
A good local builder will factor all of this in from the design stage — getting it right early avoids costly changes later.
How to Get Started
Building a granny flat is a multi-stage process, and the earlier you get expert advice, the smoother it will go:
- Check your zoning and R-Codes — visit the City of Bunbury’s website or MyPlan WA to understand what applies to your lot.
- Engage a licensed builder familiar with the South West WA region and current R-Code changes.
- Commission a site assessment — soil tests, BAL assessment, and a survey if you don’t have a current one.
- Finalise design and apply for your building permit — your builder can typically manage this process for you.
- Construction and connection — once the permit is issued, work can begin.
Talk to Element Structures About Your Granny Flat Project
At Element Structures, we work with homeowners across Bunbury and the South West WA region on granny flats, home extensions, and new builds. We’re across the current WA R-Code requirements and understand the local council processes that apply in this area.
Contact Element Structures for a free, no-obligation quote in Bunbury and the South West. Whether you’re at the planning stage or ready to build, we’d love to help you make the most of your property.