Building a granny flat in Perth is one of the smartest property decisions you can make right now — but navigating Western Australia's planning system can feel overwhelming. This guide cuts through the complexity and tells you exactly what rules apply to your property in 2025.
Quick Summary: In most Perth suburbs zoned R20 or above, you can build a secondary dwelling (granny flat) up to 60m² without needing a Development Approval, provided you meet setback and site coverage requirements. A Building Permit is always required. Our team handles all approvals — book a free site assessment to confirm what's possible on your block.
What Is a Secondary Dwelling?
In Western Australia, a "granny flat" is formally called a Secondary Dwelling under the Residential Design Codes (R-Codes). It's defined as a self-contained dwelling on the same lot as a primary dwelling, used as a residence by a person or group with a domestic or family arrangement with the primary occupants.
Key distinction: a secondary dwelling is different from a Grouped Dwelling (which requires subdivision) or an Ancillary Dwelling (older terminology). Under the 2021 R-Code revisions, "secondary dwelling" is the correct term, and it comes with specific size, setback, and approval requirements.
R-Code Requirements for Secondary Dwellings
The WA Residential Design Codes (R-Codes) are the primary planning instrument governing secondary dwellings across Perth. The requirements depend on your property's R-Code classification, which determines density and design standards.
Minimum Lot Size
To build a secondary dwelling in Perth, your lot generally needs to meet minimum size thresholds:
| R-Code Zone | Min. Lot Size | Max. Secondary Dwelling Size |
|---|---|---|
| R20 | 450m² | 60m² habitable |
| R25 | 350m² | 60m² habitable |
| R30 | 260m² | 60m² habitable |
| R40 | 200m² | 60m² habitable |
| R60+ | 150m² | 70m² (some councils) |
Note: Some local councils apply additional requirements beyond the state R-Codes. Always check your local planning scheme as well.
Maximum Size
The R-Codes cap secondary dwellings at 60m² of habitable floor area in most zones. This is net internal floor area — it excludes garage, alfresco, and outdoor areas. With a well-designed alfresco and covered outdoor living space, the total footprint can feel considerably larger than 60m².
Some councils — particularly in inner-city high-density zones — allow up to 70m². Our town planners check this as part of every free site assessment.
Setback Requirements
Setbacks define how far your granny flat must sit from the property boundaries. For Perth secondary dwellings in 2025:
Rear Setbacks
- Standard rear setback: Generally 3–6m depending on lot depth and R-Code
- Reduced rear setback: Under R-Code provisions, lots over 350m² may qualify for a 1m rear setback for single-storey secondary dwellings
- Laneway access: If your block backs onto a right-of-way (ROW), minimum setback from the ROW boundary is 1m
Side Setbacks
- R20–R30: Typically 1–1.5m each side
- R40+: Can reduce to 1m or nil boundary in some circumstances
- Nil setback: Possible under specific conditions including neighbour consent and Council approval
Important: Setback requirements are one of the most site-specific aspects of planning. They depend on your exact lot dimensions, R-Code zone, orientation, and local council overlays. Never rely on general information — our free site assessment confirms your exact setbacks within 24 hours.
Approval Pathways in 2025
There are two main approval pathways for Perth granny flats:
1. Permitted Development (No DA Required)
Under the 2021 R-Code amendments, secondary dwellings in most R-Code zones can be approved as Permitted Development — meaning no Development Approval (DA) is needed from your council, only a Building Permit.
To qualify as Permitted Development, your secondary dwelling must comply with all of the following:
- Maximum 60m² habitable floor area
- Compliant setbacks for your R-Code zone
- Compliant site coverage (typically max 50–60% of lot area)
- No more than 2 storeys
- Meets all other R-Code design requirements (overlooking, privacy, etc.)
This pathway significantly reduces approval time — from 6–12 weeks for a DA to just 3–6 weeks for a Building Permit alone.
2. Development Approval (DA Required)
A DA is required when:
- Your design doesn't meet one or more R-Code requirements (requiring a "variation")
- Your local planning scheme has additional requirements
- Your block is in a heritage area or special control area
- Council has applied a Development Contribution Area or similar overlay
DAs add 6–12 weeks to the process but can enable designs that wouldn't otherwise be possible — including reduced setbacks, increased size, or non-standard configurations.
Council-by-Council Variations
While state R-Codes set the baseline, Perth's 30+ local councils can apply additional requirements through their Local Planning Schemes. Key variations to be aware of:
- City of Perth, Subiaco, South Perth: Heritage overlays apply in many areas — additional design guidelines and sometimes Heritage Council input required
- City of Swan, City of Armadale: Streamlined DA pathways for secondary dwellings — typically 4–6 weeks
- City of Joondalup, Stirling: Very active secondary dwelling markets — council processing is well-established
- City of Fremantle: Heritage and character area overlays apply broadly — design standards are stricter
Building Permit Requirements
Regardless of whether a DA is required, all secondary dwellings in Perth require a Building Permit under the Building Act 2011 (WA). To obtain a Building Permit, you need:
- Architectural working drawings and specifications
- Structural engineering documentation
- Energy efficiency assessment (NatHERS certificate)
- Owner-Builder or Licensed Builder details
- Applicable fees (typically $800–$2,500 depending on council)
We prepare and lodge all Building Permit documentation as part of our standard fixed-price service.
Service Connections
A secondary dwelling requires separate utility connections:
- Water & sewer: Water Corporation approval required. A new meter or sub-meter can be installed.
- Electricity: Western Power connection — either from main house switchboard (most common) or separate meter
- Gas: ATCO Gas connection if applicable
- NBN: NBN Co can extend connection to granny flat — we pre-wire during construction
Service connection costs are included in our fixed-price packages — no surprise bills.
2025 Regulatory Changes
The WA government has been actively encouraging secondary dwelling construction to address Perth's housing shortage. Key 2025 developments:
- Increased density targets: Medium-density targets mean more Perth suburbs are upzoned to R30+, increasing the number of properties eligible for secondary dwellings
- Simplified application forms: WAPC has streamlined the BA1 Building Application forms for secondary dwellings
- Council coordination: DPLH (Dept. of Planning, Lands & Heritage) has issued updated guidance to councils on fast-tracking compliant secondary dwelling applications
- Short-stay accommodation: Regulations around using granny flats for Airbnb/short-stay have been clarified — owner-occupier on-site requirement still applies in most zones
Not sure about your property? Our town planning team can check your R-Code zone, lot size eligibility, setback requirements, and approval pathway for free — usually within 24 hours of your enquiry. Request a free R-Code check →
Summary: Your Quick Checklist
- ✅ Check your R-Code zone (R20, R25, R30 etc.) — available on planning.wa.gov.au or ask us
- ✅ Confirm your lot size meets the minimum threshold for your zone
- ✅ Understand your setback requirements — rear, side, and any ROW
- ✅ Determine whether your design qualifies as Permitted Development (no DA) or requires a DA
- ✅ Budget for Building Permit, structural engineering, and service connections
- ✅ Check your council's local planning scheme for any additional requirements
Mark Thompson
Co-Founder & Managing Director
Licensed builder for 22 years and co-founder of Perth Granny Flat Specialists. Mark has overseen 500+ secondary dwelling builds across Perth and is a recognised expert in WA planning regulations.