Drafting a Granny Flat in Perth: How to Make the Most of WA’s New Ancillary Dwelling Rules

Perth’s housing squeeze has pushed the State Government to overhaul the laws for ancillary dwellings, better known as granny flats. The April 2024 amendments to the Residential Design Codes (R-Codes) strip away much of the red tape that once discouraged backyard builds. If you’re weighing up whether to add a second, self-contained home behind the main house, here’s what you need to know—plus a few tips drawn from day-to-day drafting practice.

Why the rules changed

Vacancy rates below one per cent and rent rises no tenant can ignore forced the Government to hunt for “missing-middle” supply. Allowing small homes on established blocks is cheaper than opening new suburbs, and it gives owners a fresh income stream or a comfortable space for family. The reforms focus on speed and simplicity rather than density targets alone.

Key wins for homeowners

• No minimum lot size

  Leave the tape measure in the shed. Any residential parcel, even a tight 250 m² townhouse lot, can now host an ancillary dwelling provided other R-Code standards are met.

  
  

• Grouped-housing and strata inclusion

  Villas and many strata blocks can join the party, although councils often insist the lot has no shared (common) property. A quick phone call to the planning desk will confirm the position for your suburb.

  
  

• Seventy-square-metre cap, clarified

  The 70 m² limit applies to habitable rooms only. A veranda, storeroom or carport sits outside that tally, giving clever designers extra breathing room.

  
  

• Style freedom

  The old “match the main roof and brick” clause has gone. Contemporary pod construction and modular builds now slot in without an argument over colour palettes.

  
  

• Relaxed parking

  Near train lines and high-frequency buses, councils waive the extra bay. On lower-density streets, you may still need one designated space. Check the local scheme map before you finalise the site plan.

  
  

Two approvals—not one

1. Development (planning) exemption

   Tick every deemed-to-comply box—size, setbacks, height, privacy—and you sidestep a development application. That saves at least two months.

   
   

2. Building Permit—non-negotiable

   Every granny flat needs a permit under the Building Code of Australia. Most owners choose the certified (BA1) route: hire a private building surveyor for a Certificate of Design Compliance, lodge it with council, and get sign-off within ten working days. The uncertified (BA2) path puts the onus back on council officers and takes more than double the time.

   
   

Councils still matter

The R-Codes overrule local schemes where there’s a clash, yet councils keep layers of policy that can trip you up:

• Heritage precincts (Mount Lawley, Fremantle and others) always demand a full application and a respectful façade.

• Bushfire-prone hills suburbs need a BAL report and construction upgrades that lift cost and complexity.

• Rural shires may let you nudge the floor area to 100 m² but insist you build close to the main house to avoid future subdivision claims.

Because many fact sheets haven’t caught up with the April changes, speak to a planner directly rather than trusting the download you found online.

Counting the dollars

A turnkey one-bedroom unit in Perth now sits around $160–180k, while a two-bedroom version usually lands between $170k and $200k. Add site works, service trenches and council levies and the total budget can push beyond $250k, especially on sloping ground. Weekly rents of $400–$550 are common in middle-ring suburbs, so yields remain attractive, yet don’t forget the future Capital Gains Tax bite once part of the home becomes an income-producer. A short chat with a qualified accountant before you pour the slab is cheap insurance.

Design choices that pay off

Good planning turns 70 m² into a liveable retreat rather than a glorified bedsit.

• Open interiors and high ceilings create volume without extra floor area.

• North-facing living and wide eaves slash energy bills and meet the NatHERS score with fewer upgrades.

• Sliding doors to a deck extend the living zone and, crucially, don’t count toward the size cap.

• Careful window placement guards privacy for both dwellings; no-one wants to share breakfast via a side-fence stare.

• Tuck storage into every cavity—wall-to-wall robes, overhead kitchen cupboards, even a seat with a lift-up lid at the entry.

Where mobility is a concern, widen doorways, drop shower hobs and allow turning circles. Some hills shires reward accessible design with an extra 10 m² of floor space.

Picking the right drafting and build team

Specialist granny-flat contractors now dominate the market, but they vary. Always:

• Confirm the builder’s registration and home indemnity cover.

• Demand a fixed-price scope that lists all items—including power upgrades, sewer tie-ins and basic landscaping.

• Ask for previous clients’ details and walk through a finished project.

  
  

Engaging an architectural design service Perth firm or an experienced home design drafting consultant early can iron out compliance questions before they cost money. For owners juggling an extension at the same time, bundling the job under one renovation drafting brief often trims fees.

Common traps and how to dodge them

Trap	How to avoid it
Building before the permit	Wait for the stamped BA1 and stick it on site—inspectors do check.
Under-budgeting site works	Order a geotechnical report and a feature survey up-front.
Privacy complaints	Use screening, angled windows and separate access paths.
Shared bills disputes	Install water and power sub-meters from day one.

Final thoughts

The 2024 reforms turn a once daunting process into a realistic weekend project for many Perth owners. Treat the granny flat as part of the wider property, not an add-on, and lean on professionals where rules get murky. A brief design consultation with domestic drafting service Perth specialists or house plan designers near me may cost a few hundred dollars, yet it can save months and thousands of dollars down the track. With clear goals, sound advice and a solid budget buffer, a backyard home can ease Perth’s housing stress and boost your own bottom line at the same time.