Granny flat rules in WA: what flippers can build and rent out

A granny flat is one of the cheapest ways to add rent and resale value to a flip without splitting the block or waiting out a long approval. The granny flat rules in WA changed in April 2024, when the state stripped out the minimum lot size and the planning-approval step for compliant builds, so a modest second dwelling now sits on the table for far more blocks than it used to. But the win only shows up if your build and your site meet the criteria, and there is still a building permit to clear, so it pays to know exactly what you can put up before you price it into a deal.

So before you build a second dwelling into your feasibility, it is worth knowing what Western Australia now lets you do without a planning application, where the 70m² line sits, and the site conditions that quietly disqualify a block that looks fine at a glance. This is general information, not planning advice, but it will tell you what to check and which questions to take to your local council or a building surveyor.

Granny flat rules in WA, in plain English

In Western Australia a granny flat is officially an ancillary dwelling: a self-contained home on the same lot as a single house, with its own kitchen, bathroom and living area. It is subordinate to the main house and stays on the one lot, which means it cannot be sold off or strata-titled on its own without going through a separate subdivision. It is a second home on one block, not a second block.

Two things make WA one of the friendlier states for this. First, an ancillary dwelling can be rented to anyone. The old restriction that tied occupation to a family member is gone, so a compliant granny flat can be let to a tenant on the open market and become a real second income stream on a single title. Second, and this is the big one, a compliant build no longer needs planning approval at all.

What the April 2024 R-Codes reform changed

The change that matters to flippers came into effect on 10 April 2024, when the state government amended the Residential Design Codes (the R-Codes) to boost housing supply. Three parts of that reform move the numbers on a deal.

The headline change is that the minimum 350m² lot size requirement was scrapped. Before the reform, an ancillary dwelling was effectively restricted to larger blocks. Now an R-Code-compliant granny flat can go on a residential lot of any size, provided it meets the setback rules, and the exemption was extended to grouped dwellings and strata lots across all the density codes.

The second change is the one that saves you the most time: since 10 April 2024, a compliant ancillary dwelling up to 70m² does not need planning approval. If your design meets every relevant deemed-to-comply requirement of the R-Codes, you skip the discretionary planning application entirely and go straight to a building permit. The third change trims the build itself, because an ancillary dwelling is no longer required to provide a car parking bay in most cases, and the old provision forcing the granny flat to match the colour, roof pitch and materials of the main house was deleted.

The catch worth stating plainly: none of this removes the building permit. Every ancillary dwelling still needs one so the structure meets the building code and engineering standards before you start. Skipping planning approval is not the same as skipping approval altogether.

The deemed-to-comply numbers that decide it

To land on the no-planning-approval pathway, your granny flat has to meet the deemed-to-comply requirements of the R-Codes. The exact figures sit in your local planning scheme, so confirm them against your council for your address rather than assuming, but the shape is consistent:

• A floor area of 70m² or less. This is the enclosed living area. Verandahs, patios and carports usually sit outside that number, so you can often add covered outdoor space without eating into the cap. Go over 70m² and you lose the exemption and drop back into a discretionary planning application.
• Setbacks that meet your local scheme. This is the requirement that most often bites on tight blocks, because the ancillary dwelling has to sit within the boundary setbacks the R-Codes and your council set. Design to the setbacks first, then size the dwelling to fit.
• On the same lot as the existing single house, and subordinate to it. One primary house, one ancillary dwelling on the one title.
• Open space and site cover for your zone. The R-Codes still expect a share of the lot to stay as open space once both dwellings are built, so a small inner-Perth block can run out of room even when everything else checks out.

Miss one of those and you are not blocked, you are just into a planning application, which you should price as extra time and a less certain outcome. Note too that many WA councils will approve a granny flat larger than 70m², sometimes up to 100m² or more, but that is a discretionary planning decision rather than the fast deemed-to-comply lane, so treat the bigger build as a separate, slower path.

What an ancillary dwelling does for rent and resale

The reason a granny flat earns its spot in a feasibility is that it can pay off on both exits at once. Now that it can be self-contained and let to anyone, a compliant ancillary dwelling adds a second rental income to one title, and on resale a proper second dwelling can lift the after-repair value in suburbs where buyers pay for dual-income or multi-generational living.

What I will not do is hand you a "granny flats add $X" figure, because that is entirely local. The uplift depends on your suburb's rental demand, the quality of the build and what comparable dual-dwelling homes have actually sold for nearby. Treat the added rent and the resale bump as inputs to test, not a given, and remember the build cost comes off the top. Run the granny flat as one option against the others, a straight cosmetic flip, a bigger reconfiguration, or just holding, and let the numbers pick the winner. That head-to-head is exactly what our feasibility tool is built for, so you are comparing real figures rather than backing a hunch.

The overlay and site traps that quietly kill it

A block can clear the 70m² and setback tests and still cost you, because the site itself carries constraints that the R-Codes sit on top of. In Western Australia the usual suspects are bushfire-prone areas, which are mapped by DFES and can trigger a Bushfire Attack Level assessment and extra construction requirements, and flood or drainage constraints, where levels and stormwater come into play. Heritage listings and character-area provisions can pull a build back into a discretionary assessment or add design controls, which matters across Perth's older inner suburbs and the Wheatbelt towns.

The title can carry surprises too, from easements to restrictive covenants that limit where, or whether, you can build a second dwelling, and covenants are common across newer WA estates. Read the certificate of title and any encumbrances properly before a deal that leans on a granny flat. And because the rules are genuinely different in every state, never carry an interstate assumption across the border: the NSW granny flat rules, the QLD granny flat rules, the VIC granny flat rules and the SA granny flat rules all approve secondary dwellings on completely different tests. If the block's real upside is splitting it rather than building on it, that is a separate maths problem, and granny flat vs subdivision compares which one actually makes more money.

Check your block, then run the numbers

You can get most of the way fast. Confirm the build comes in at 70m² or less, check that it sits inside your council's setbacks with enough open space left over, and confirm there is nothing in a bushfire, flood, heritage or character control, or a covenant on the title, that pushes you into a planning application. If that is all clear, a granny flat is on the table without a planning approval, and worth a proper feasibility.

One honest note on the tool. Our live zoning and overlay data currently covers NSW, VIC and QLD, not Western Australia, so for a Perth or regional WA block you will confirm the zone, setbacks and overlays yourself with the council or a building surveyor. What travels anywhere is the maths: drop your purchase price, build cost, rent and resale into the feasibility tool and test the granny flat option against a straight flip before you commit. And if you are new to the whole process, the complete guide to flipping a house in Australia puts the granny flat move in the context of the deal as a whole.

Granny flats reward the boring homework. Get the 70m² cap, the setbacks, the open space and the overlays checked up front, know whether you are deemed-to-comply or heading for a planning application, and the second dwelling becomes a clean line in your feasibility instead of a surprise that never gets approved.

This is general information only and not planning, financial or legal advice. Ancillary dwelling rules in Western Australia are set by the Planning and Development Act 2005 and the Residential Design Codes (as amended in April 2024) and can be affected by the setbacks, overlays and encumbrances on your specific block, and by your local planning scheme, and the rules change over time. Always confirm the current rules for your site with the council, a registered building surveyor or a planning professional before you buy or build.

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