WA Granny Flat Requirements 2026: Rules, Size & Approval Guide
Building a granny flat in Western Australia (WA) is now much easier for homeowners. Stop waiting for permits! In April 2024, the WA Government announced major changes to the planning rules. Discover the 70m² rule, new rental laws, and how to build today. Check size limits, approval rules, setbacks, rental laws and building requirements before you start.
These units are officially called Ancillary Dwellings. Consequently, you can now build a small home in your backyard without the long wait for council approvals.
However, you must still follow the Granny Flat requirements in WA to ensure your build is legal. This 2026 guide covers everything you need to know about the latest rules.
Granny flat requirements WA: No Minimum Lot Size
The biggest news for WA homeowners is the removal of the minimum lot size. Previously, you needed at least 450m² of land to build a granny flat. Luckily, the government has scrapped this rule.
Therefore, you can now build a granny flat on almost any residential block, no matter how small it is. This change helps more people create space for family or renters in busy areas like Perth.
Can you build a 70sqm granny flat in WA?
While lot size is no longer an issue, the size of the unit itself still has limits. Specifically, you must meet these granny flat size requirements in WA:
- Maximum Floor Area: The internal living space cannot exceed 70m².
- Extra Spaces: Patios, verandas, and carports usually do not count towards the 70m² limit.
- Large Lots: If your land is very large (over 1,100m²), some councils may allow you to build up to 100m².
Rural & Large Lot Exceptions
If your property is in a rural zone or on a large residential lot (typically over 1,100 m²), the rules can be even more flexible. While the standard limit is 70m², many local Shires in Western Australia allow granny flats to be as large as 100m² or even 120m².
Tip: If you are in an area like the Shire of Williams, always check their specific Local Planning Scheme, as rural setbacks and size allowances often differ from urban Perth requirements.
What size block do you need for a granny flat in WA?
You no longer need a minimum block size to build a granny flat in WA. This change makes it possible for many homeowners to add a flat even on smaller lots.
However, the flat must still fit safely on the land and comply with setback and open space rules. You should also consider how much space is left for your backyard, access paths, and landscaping.
A well-planned site layout can make even a small block feel open and functional while staying within council rules.
Do you need planning approval for a granny flat in WA?
In most cases, you do not need planning approval to build a granny flat in Western Australia. Recent planning changes allow flats up to 70 sqm to be built without council approval, as long as they meet standard rules like setbacks, height limits, and privacy requirements.
Even though planning approval is often not required, you still need a building permit. The building permit ensures the flat is safe and meets all construction standards.
There are some exceptions where planning approval may still be required:
- The flat is larger than 70 sqm
- The site is in a heritage or environmentally sensitive area
- The design does not follow the standard R‑Code requirements
For most homeowners, these rules make it much easier to add a granny flat to their backyard. Always check with your local council to confirm that your project meets all requirements before starting construction.
For design ideas that fit the 70 sqm limit, see our 70sqm Granny Flat Plans WA.
Requirements for Owner-Builders
If you hold an owner-builder license, you have the advantage of managing the construction yourself. However, you must still adhere to these steps:
- Building Permit: Even if planning approval isn’t needed, a Building Permit is mandatory to ensure the structure meets the National Construction Code (NCC).
- Approval for Works: You must obtain “Owner-Builder Approval” from the WA Building Commission for any project valued over $20,000.
- Sustainability: Ensure your design meets the latest 2026 energy efficiency ratings, which are now strictly enforced for all new builds in WA.
Can you rent out a granny flat in WA?
WA is a very “renter-friendly” state for granny flats. Unlike some other parts of Australia, you have a lot of freedom here.
Anyone Can Live
You can rent your Ancillary Dwellings to a family member or a private tenant.
Extra Income
You do not need special permission to list your granny flat on the rental market.
No Extra Parking
Most properties in WA do not need to provide a new car parking spot for the tenant.
If you are planning to rent out your granny flat and want to maximise your rental income, follow our [Rental Series To Maximise Your Property Value].
Setbacks and Placement
You must still be careful about where you place the unit on your land. For instance, you must follow “setback” rules. This is the distance between the granny flat and your neighbour’s fence.
- Behind the House: Usually, the unit must be placed behind the front line of your main house.
- Privacy: Moreover, you must ensure your windows do not look directly into your neighbour’s backyard or living room.
How close can a granny flat be to a boundary in WA?
Setback rules define how far a granny flat must sit from property boundaries. These rules protect privacy and sunlight access for neighbours.
In WA, most councils require a minimum setback of 1.5–2 meters from the side and rear boundaries. Front setbacks often match the existing building line or council zoning.
Check your local council for exact distances. A careful site plan can help you maximise backyard space while complying with the rules.
How much does it cost to meet granny flat requirements WA?
Meeting WA requirements adds costs beyond construction. Homeowners should budget for:
- Approvals: CDC or DA fees, depending on your block and pathway
- Site reports: Soil tests, bushfire, flood or structural reports
- Utility connections: Water, electricity, and sewer may need upgrades
These costs vary based on your location, block condition, and builder. For a full breakdown of building and approval costs, see our WA Granny Flat Cost 2026 article.
Pro tip: Include these costs in your budget early to avoid surprises.
Design and Materials
The WA government wants granny flats to look good and last a long time. Specifically, you must follow these design rules:
- Matching Style: The design and colours should suit your main house.
- New Materials: You are generally not allowed to use second-hand materials for the main structure.
- Sustainability: New builds in 2026 must meet modern energy efficiency standards. Consequently, your granny flat will be cheaper to keep cool during the hot Perth summers.
Check our detailed guide on [Granny Flat Designs in Australia 2026]. See the 5 top designs that you can build on your space.
Off-Grid Living: Solar & Water Tanks
Building in rural WA often means you are far from main utility lines. The 2026 regulations fully support “Off-Grid” ancillary dwellings:
- Solar Power: You are permitted to install standalone solar arrays and battery storage to power your unit.
- Water Supply: For properties without a mains water connection, installing dedicated water tanks is standard practice.
- Bushfire Safety: Note that in rural zones, a specific water tank (often 10,000L to 20,000L) with a specialised “firefighter coupling” may be required to meet BAL (Bushfire Attack Level) safety standards.
Frequently Asked Questions (FAQs)
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