Granny Flat Rules WA: Ancillary Dwelling Size, Approval & R-Codes Guide (2026)
WA granny flat rules explained. 70sqm ancillary dwelling limits, R-Code reforms removing lot size minimums, approval exemptions and rental rules.
TL;DR: Western Australia overhauled its granny flat rules in April 2024. The minimum lot size requirement has been scrapped — you can now build an ancillary dwelling (granny flat) up to 70sqm on any residential lot without planning approval, provided you meet the R-Code deemed-to-comply standards. Granny flats are now also permitted on grouped dwellings and strata lots, not just single houses. You can rent to anyone. A building permit is still required, but removing the planning approval step saves weeks and thousands of dollars.
Key takeaways
- Since 10 April 2024, the minimum lot size for granny flats in WA has been removed. Previously you needed at least 350sqm.
- Maximum floor area is 70sqm internal living area.
- If your granny flat meets R-Code deemed-to-comply provisions, no planning (council) approval is required.
- Granny flats are now permitted on grouped dwellings and strata lots in all R-Codings, not just single house lots.
- Design compatibility with the main dwelling is no longer required.
- Car parking is only required if the property is more than 800m from a train station or 250m from a high-frequency bus route.
- A building permit is always required.
What changed in April 2024?
The Cook Labor Government introduced major amendments to the Residential Design Codes (R-Codes) Volume 1 that took effect on 10 April 2024. The intent was to boost housing supply by making granny flats easier to build on more properties.
Before April 2024, WA required a minimum lot size of 350sqm, ancillary dwellings were only permitted on single house lots, designs had to be visually compatible with the main dwelling, a parking bay was mandatory in most cases, and many compliant designs still needed planning approval.
After April 2024, the minimum lot size was removed entirely, grouped dwellings and strata lots became eligible across all R-Codings, design compatibility is no longer assessed, parking near public transport is not required, and compliant designs are exempt from planning approval.
These changes opened up a large number of Perth properties that were previously ineligible.
What is an ancillary dwelling?
In WA planning terminology, a granny flat is called an ancillary dwelling. Under the R-Codes, an ancillary dwelling is a self-contained dwelling on the same lot as a single house or grouped dwelling, subordinate to the main dwelling, located behind the street setback line, and capped at 70sqm internal floor area. It must not prevent the main dwelling from meeting required open space and outdoor living area standards.
The ancillary dwelling must have its own kitchen, bathroom, bedroom, and separate entry. It shares the same certificate of title as the main property and cannot be subdivided or sold separately.
Size limits: the 70sqm cap
WA’s maximum floor area for an ancillary dwelling is 70sqm of internal floor area. Compared to the other mainland states:
| State | Max floor area |
|---|---|
| WA | 70sqm |
| NSW | 60sqm |
| Victoria | 60sqm |
| QLD (Brisbane) | 80sqm |
The 70sqm cap comfortably fits a 2-bedroom layout with open-plan kitchen/living, bathroom, and laundry. Common configurations within 70sqm include:
- 1 bedroom + study: spacious living area with a dedicated home office
- 2 bedroom: standard layout with good-sized rooms
- 2 bedroom + small study: compact but workable
2-bedroom granny flats in WA: price guide
Two-bedroom configurations are the most popular in WA. Typical pricing in 2026:
| Build type | Price range | Notes |
|---|---|---|
| Basic kit/flat-pack | $60,000-$90,000 | Supply only, owner-builder assembly |
| Standard turnkey | $120,000-$160,000 | Builder-managed, standard finishes |
| Mid-range turnkey | $160,000-$200,000 | Quality finishes, better insulation |
| Premium custom | $200,000-$260,000 | Architect-designed, high-end finishes |
Add $15,000-$40,000 for site works, services connections, and permits. Use our granny flat cost calculator for a personalised estimate based on your Perth suburb.
Planning approval: when you need it and when you don’t
No planning approval required if:
Your ancillary dwelling meets all deemed-to-comply provisions under R-Codes Volume 1:
- Internal floor area does not exceed 70sqm
- Located behind the street setback line
- Meets all setback requirements (Tables 2A and 2B of the R-Codes)
- Meets site coverage requirements
- Meets visual privacy requirements
- Does not prevent the main dwelling from meeting required open space and outdoor living area
- The property is in a residential zone
If all these criteria are met, you go directly to the building permit stage with no planning application needed.
Planning approval IS required if:
- The dwelling exceeds 70sqm internal floor area
- It doesn’t meet deemed-to-comply setback, site coverage, or height requirements
- The property is in a heritage area or has environmental constraints
- Local planning policies impose additional restrictions beyond the R-Codes
- The design would cause unacceptable privacy, overshadowing, or access impacts on neighbours
When planning approval is required, you must lodge a Development Application (DA) with your local council, assessed against the R-Codes and any applicable local planning policies.
Setback requirements
WA setback rules for ancillary dwellings follow the same provisions as other residential buildings under the R-Codes. The specific distances depend on the R-Coding of your lot (e.g., R20, R25, R30, R40, R60), boundary wall length and height, and whether the wall has major openings (windows or doors).
Setback distances are in Tables 2A and 2B of R-Codes Volume 1. As a general guide:
| Wall type | Typical setback |
|---|---|
| Wall with no major openings, up to 3.5m high, up to 9m long | Nil (on boundary) in many R-Codings |
| Wall with no major openings, over 3.5m high | 1.0-1.5m |
| Wall with major openings | 1.5-6.0m depending on height and R-Coding |
| Rear boundary | 1.0-6.0m depending on R-Coding |
These are general guides. The exact setback for your property depends on your R-Coding and wall configuration — always check Tables 2A and 2B or consult your local council.
Street setback
The ancillary dwelling must sit behind the street setback line. In most Perth suburban areas, this is typically 6-9m from the primary street boundary, though it varies by council.
Height limits
For most suburban residential areas (R20-R40):
- Maximum wall height: 6m (two storeys)
- Maximum roof height: 9m
Most granny flats in Perth are single storey, with wall heights of 2.7-3.5m and overall heights of 3.5-5.0m. This keeps costs down and reduces privacy impacts on neighbours. Higher R-Codings (R60+) allow greater heights, but the 70sqm floor area cap means most designs stay single storey anyway.
Car parking
Under the April 2024 reforms, parking requirements have been significantly relaxed:
- No additional car parking required if the property is within 800m of a train station or 250m of a high-frequency bus route
- One additional space required for all other locations
This recognises that many Perth properties near public transport simply don’t have room for extra parking, and the old requirement was blocking otherwise feasible projects.
Visual privacy
The R-Codes include visual privacy requirements that apply to ancillary dwellings:
- Habitable rooms with major openings (living rooms, bedrooms) that overlook neighbouring properties must meet minimum setbacks or use privacy screening
- Elevated outdoor areas within cone-of-vision distance must be screened
- Privacy requirements increase with building height
For single-storey granny flats at ground level, visual privacy is rarely a problem. It becomes more relevant for designs with elevated living areas or on sloping sites.
Grouped dwellings and strata lots
Extending eligibility to grouped dwellings and strata lots was one of the more significant April 2024 changes. Previously, ancillary dwellings were only permitted on single house lots.
If you own a townhouse or villa on a strata lot, you can now build a granny flat subject to meeting all R-Code deemed-to-comply provisions, strata by-laws allowing construction (check with your strata company), sufficient lot area for the dwelling plus required open space, and the strata lot being individually titled rather than common property.
This opens up granny flat opportunities for a large segment of Perth homeowners who were previously excluded.
Rental rules
You can rent an ancillary dwelling to anyone in WA. There is no restriction on the relationship between the occupant and the owner. The tenant can be a family member, a stranger from the open market, or a short-term tenant (subject to any local short-stay accommodation rules).
Standard WA residential tenancy laws under the Residential Tenancies Act 1987 apply. The granny flat must have a final building approval (occupancy permit or certificate of building compliance) before being occupied.
Transitional provisions: April 2026 deadline
Local planning frameworks that modify R-Codes Volume 1 (2024) provisions must be reviewed, amended, and approved by 10 April 2026. If a council has not updated its local planning framework by that date, the R-Codes Volume 1 provisions prevail over any conflicting local policies.
This means some councils that currently have stricter-than-R-Code requirements may have those restrictions effectively overridden from April 2026 if they haven’t completed their review.
If your council currently imposes additional restrictions beyond the R-Codes, those restrictions may no longer apply from April 2026. The deemed-to-comply provisions become the baseline. Check with your council to confirm whether their local policies have been updated.
Costs: what will a WA granny flat cost?
| Cost component | Planning exempt | DA required |
|---|---|---|
| Planning/DA fees | $0 | $2,000-$5,000 |
| Building permit | $2,000-$4,000 | $2,000-$4,000 |
| Design and plans | $3,000-$8,000 | $5,000-$12,000 |
| Engineering | $1,500-$3,000 | $1,500-$3,000 |
| Construction (standard 2-bed) | $120,000-$160,000 | $120,000-$160,000 |
| Site works and services | $15,000-$40,000 | $15,000-$40,000 |
| Total estimate | $141,500-$215,000 | $145,500-$224,000 |
Perth’s construction costs tend to run slightly below Sydney or Melbourne, helped by flatter terrain, easier site access, and a competitive builder market. Use our granny flat cost calculator for a personalised estimate.
Common mistakes to avoid
- Assuming the old 350sqm minimum still applies — it was removed in April 2024. Any residential lot is now eligible.
- Using the wrong R-Code setback table — deemed-to-comply setbacks vary by R-Coding. Using the wrong values can make an “exempt” project non-compliant.
- Forgetting strata approval — if you’re on a strata lot, your strata company must approve the construction even if planning approval isn’t required.
- Putting the granny flat in front of the setback line — it must be behind the street setback. Front-of-lot designs aren’t permitted.
- Not checking local planning policies — until April 2026, some councils may still have requirements beyond the R-Codes that apply to your property.
Perth suburb considerations
Feasibility varies across Perth based on typical lot sizes and R-Codings:
| Area | Typical lot size | R-Coding | Granny flat feasibility |
|---|---|---|---|
| Inner suburbs (e.g., Mt Lawley, Subiaco) | 400-700sqm | R20-R40 | Good — smaller lots now eligible after minimum lot size removal |
| Middle suburbs (e.g., Morley, Cannington) | 600-900sqm | R20-R30 | Excellent — ample space, standard setbacks |
| Outer suburbs (e.g., Joondalup, Rockingham) | 500-800sqm | R20-R25 | Excellent — generous lots, competitive build costs |
| Hills suburbs (e.g., Kalamunda, Mundaring) | 1,000sqm+ | R5-R10 | Good — large lots but steeper site works costs |
Frequently asked questions
Do I need council approval for a granny flat in Perth?
Not if your granny flat meets all deemed-to-comply provisions in the R-Codes, including the 70sqm cap, setbacks, site coverage, and visual privacy requirements. A building permit is always required.
What is the maximum size for a granny flat in WA?
The maximum internal floor area is 70sqm under the R-Codes. Proposals over 70sqm require planning approval from council.
Can I build a granny flat on a small lot in Perth?
Yes. Since April 2024, there is no minimum lot size. You still need to meet setback, site coverage, and open space requirements, which can be tight on very small lots.
How much does a 2-bedroom granny flat cost in WA?
A standard turnkey 2-bedroom granny flat in Perth typically costs $120,000-$160,000 to build, plus $20,000-$45,000 for site works, permits, and connections. Total project cost is usually $140,000-$215,000.
Can I rent out my granny flat in WA?
Yes. There are no restrictions on who can live in an ancillary dwelling. You can rent to anyone under standard WA residential tenancy laws.
Do I need a car parking space for my granny flat?
Only if your property is more than 800m from a train station and more than 250m from a high-frequency bus route. Properties near public transport are exempt from the additional parking requirement.
This guide reflects WA granny flat rules as of April 2026. Regulations can change — always verify current requirements with your local council or Planning WA before starting your project. Use our granny flat cost calculator to estimate your build costs.
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