Ultimate Guide to Building a Granny Flat WA 2026 Reforms

Building a Granny Flat WA (officially known as an Ancillary Dwelling) has never been easier. Following the landmark 2024 planning reforms, Western Australia has become one of the most flexible states for secondary dwellings. Whether you are looking to house a family or generate rental income in Perth’s booming market, this guide covers everything you need for 2026.

Key Rules for Granny Flat WA (2026)

The Western Australian government recently slashed red tape. Here are the “must-know” rules:

No Minimum Lot Size

Previously, you needed 350m² or 450m². Now, you can build a granny flat on almost any residential lot, regardless of size, as long as it fits the R-Code requirements.

The 70m²
Limit

The maximum internal floor
The area is 70m².
Pro Tip:
This does not include your verandah,
patio, or carport!

Planning Exemptions

If your design is “Deemed-to-Comply” with the Residential Design Codes (R-Codes), you do not need a planning permit.
You only need a Building Permit.

Understanding granny flat WA R-Codes & Setbacks

In WA, your build is governed by R-Codes. These determine how much of your backyard you can cover.

  • Setbacks: Generally, you need to keep a small distance from your neighbour’s fence (usually 1m to 1.5m depending on wall height and length).
  • Parking: Good news! In most Perth metro areas (near high-frequency bus or train lines), you do not need to provide an extra parking spot for the granny flat.

Rental Laws & Income Potential

Can you rent out a Granny Flat in WA to anyone? Yes!

Unlike some other states in the past, WA allows you to rent your secondary dwelling to private tenants, students, or short-term guests (Airbnb).

2026 update!

If you plan to use it for short-term rental (STRA), ensure you are registered on the WA State-wide Register.

Estimated Construction Costs in WA

Building costs in Perth and regional WA vary based on the method:

  • Flat-pack/Kit Homes: $80,000 – $110,000
  • Modular/Prefab: $120,000 – $170,000
  • Custom Brick Build: $190,000+
See Full Cost Breakdown
Detailed cost breakdown for building a granny flat in WA, comparing budget kit homes, mid-range modular units, and premium custom brick builds.

frequently asked questions

In Western Australia, the maximum allowed internal floor area for a granny flat (Ancillary Dwelling) is 70m². However, this 70m² limit only applies to the enclosed living space. You can often add additional outdoor areas like verandahs, patios, or carports without these counting towards the size restriction, provided they comply with your local council’s site coverage rules.

Under the 2024 WA planning reforms, you generally do not need a planning permit if your granny flat design meets all the “Deemed-to-Comply” requirements of the Residential Design Codes (R-Codes). You will, however, always require a Building Permit to ensure the structure meets Australian safety and engineering standards before construction begins.

No. Recent changes to the WA planning system have removed the minimum lot size requirement. You can now build a granny flat on almost any residential-zoned property, including strata lots and smaller suburban blocks, as long as you maintain the required open space and setbacks specified for your property’s R-Code.

Yes. Western Australia has some of the most flexible rental laws in Australia. You are legally allowed to rent out your granny flat to private tenants, family members, or even use it as a short-term rental (like Airbnb), provided it is a self-contained unit with its own kitchen and bathroom facilities.

While it varies by suburb, a well-designed granny flat in WA can increase property value by 15% to 25%. In the current Perth rental market, they also offer high yield potential, often paying for their own construction costs within 5–7 years through consistent rental income.

Start Your Granny Flat with a Journey Now.

From rental income to multigenerational living, we help you make the most of Western Australia’s flexible building laws.


While [Granny Flat Queensland] rules allow up to 80m², WA focuses on a more compact 70m² design

View WA Design Gallery

Found the Rules? Now, let’s make it a Reality!