The rule is about size, not bedrooms
WA's R-Codes don't set a maximum number of bedrooms for a granny flat (the official name is "ancillary dwelling"). What they limit is the size: 70 m² of internal floor area if you want to skip planning approval. The state's own explanatory guidelines say 70 m² "allows for a single or two-bedroom dwelling".
Fitting two bedrooms into 70 m²
The 70 m² is measured from the inside face of the walls, so the wall thickness doesn't count against you. Even so, two bedrooms, a bathroom, a kitchen and a living area is a tight fit. Good designs usually:
- combine the kitchen, living and dining into one open space
- keep hallways short or skip them
- put the laundry inside the bathroom
- use built-in robes instead of walk-in ones
Check your design with the granny flat 70 m² calculator.
What else the rules expect
- A kitchen and bathroom. A granny flat is self-contained, so a separate kitchen and bathroom are generally expected. The guidelines say a laundry isn't essential for planning.
- Setbacks, site cover, height and privacy. It must meet the deemed-to-comply rules for your lot, as well as the size limit.
- Parking. In most cases no extra parking bay is needed, except in some densities and places far from public transport.
- No separate title. A granny flat can't be subdivided off as its own lot.
Going over 70 m²
A bigger flat isn't automatically refused, but it no longer meets the deemed-to-comply rules. That means you need planning approval, and councils vary in what they'll accept.
A building permit is still needed
Whatever the number of bedrooms, the state is clear: you still need a building permit from your council, and the flat must meet the National Construction Code. See the full granny flat approval process or the granny flat rules in WA.