Can I build a granny flat in Bunbury without development approval? Often, yes. According to the WA Government, a granny flat (an ancillary dwelling) up to 70 m2 that meets the R-Codes deemed-to-comply rules has needed no development approval since 10 April 2024. You still need a building permit, and you should check with the City of Bunbury or your shire that the exemption applies to your lot.
This guide is for homeowners in Bunbury, Australind, Eaton, Dalyellup, Capel, Harvey, Donnybrook and Collie who want a second small home on the block: for a parent, an adult child, a carer or a tenant. The problem in the South West is rarely the rules. It is finding a builder with time for a small job while larger housing and resource projects keep local trades busy.
What changed in the WA granny flat rules
- Up to 70 m2 with no development approval, if the design meets the deemed-to-comply rules.
- No minimum lot size of 350 m2 any more.
- The granny flat no longer has to match the main house in style or materials.
- A building permit is still needed in every case.
Outside the City of Bunbury, the same state rules apply through the local planning scheme of each shire, such as the Shire of Harvey, the Shire of Dardanup and the Shire of Capel. Rural and special zones can carry extra conditions, so ask before you commit to a design.
Why modular fits a South West block
A modular granny flat is built as finished steel-framed modules, then trucked to your lot and craned onto footings. The work on your land comes down to footings, services, the lift and the connections.
For the South West this matters in two ways. Local builders can take on a small home without tying up a crew for months. And the weather that slows a timber frame on site in a wet Bunbury winter does not stop work on modules under cover in the factory.
What EcoPrestige supplies
As the manufacturer, EcoPrestige is responsible for every module: built and inspected in an offsite factory to Australian engineering and QA, then delivered to site. Each granny flat arrives with the kitchen, bathroom, laundry, linings, windows and electrical rough-in fitted, ready for a local builder to connect.
- Engineered structural steel modules sized for truck delivery.
- A bill of quantities so your builder can price the site works.
- Lifting points and an install sequence for the crane crew.
- Supply price quoted for your site, after we have seen the block.
The design and permit package is set out on our Domestic Program page.
What does not fit
- Tight backyards: if a truck cannot reach the street frontage and a crane cannot set up within reach of the pad, modules may not work.
- Bushfire prone areas: many lots around the Ferguson Valley, Collie and the hills need a bushfire assessment, which can change materials and setbacks.
- Flood or low-lying land: parts of the coast and river flats may need higher floor levels.
- Heritage areas: heritage listing or local heritage areas add planning steps.
- Steep slopes: sloping lots need taller footings or retaining, which adds site cost.
Our installation and crane guide explains access and pad preparation in more detail.
The approval path in WA
We design and draft your home, then coordinate engineering, the energy rating and certification. In Western Australia, building design is not a registered category. A registered building surveying contractor checks the plans and signs the certificate of design compliance, and the local government issues the building permit. Building engineers must be registered from 1 July 2027. A granny flat is typically Class 1a, confirmed by your building surveyor. Read how building permits work for modular buildings for inspections and sign-off. Always confirm with your building surveyor or certifier.
The programme: factory and site in parallel
The Domestic Program runs in two steps. Step 1 is feasibility on your site: zoning, access, services and a concept that fits. Step 2 is design, permits and build by the practitioners WA requires. Once the permit is in place, the modules are made in the factory while the builder prepares footings and services on your lot. Because both happen at once, time on site is shorter. The builder on site is your own builder or a local South West builder using our bill of quantities.
What to send us
- 1. The street address and certificate of title.
- 2. Who the granny flat is for and how many bedrooms you want.
- 3. Photos of the backyard, the side access and the street frontage.
- 4. Whether the lot has sewer or a septic system.
- 5. Any bushfire, flood or heritage notice you already hold.
- 6. Your builder’s name, if you already have one.
Comparing options? See transportable buildings in Western Australia and our page on modular construction in Perth.
Update, November 2026: WA’s draft R-Codes propose raising the granny flat limit from 70 m2 to 90 m2. The 70 m2 limit applies until the draft is finalised. See what the draft R-Codes propose.
Frequently asked questions
Do I need development approval for a granny flat in Bunbury?
Usually not, if it is 70 m2 or less and meets the R-Codes deemed-to-comply rules, according to the WA Government. Check with the City of Bunbury or your shire that the exemption applies to your lot. A building permit is still needed.
Does a South West granny flat have to match my house?
No. Since the WA changes of 10 April 2024, a granny flat no longer has to match the main house, and there is no minimum lot size of 350 m2.
Who builds the granny flat on my block?
EcoPrestige manufactures the modules. Your own builder or a local South West builder installs them and does the site works, using our bill of quantities.
Rules last checked: 29 October 2026. Confirm with your council and building surveyor or certifier.
Send us your Bunbury or South West block
Send the site, the use and any drawings to prebuilt@ecoprestige.com.au or download our technical brochures.