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How much does a granny flat cost in WA?

The honest answer, with every cost on the table. A complete Peak home starts at $159,500 including GST. Here's what that covers, and the three other costs to plan for.

By Peak Modular, Busselton · Updated 24 October 2026

1. The home itself

HomeRoomsSizeHome+ deck+ deck + patio
The Ridge1 bed · 1 bath41.4 m²$159,500$178,200$190,300
The Cape1 bed · 1 bath45 m²$170,500$189,200$201,300
The Headland2 bed · 1 bath70 m²$229,900$248,600$260,700
The Point2 bed · 2 bath70 m²$247,500$266,200$278,300

All prices include GST. The Reserve and The Pearl are the same price as The Ridge.

Every Peak home is built complete in our Busselton factory: complete kitchen, complete bathroom, cabinetry throughout, flooring, internal linings and finishes, and external cladding, windows and doors. Appliances and air conditioning are not included and are quoted separately.

2. A deck and patio, if you want one

The deck is where most of the living happens: morning coffee, long lunches, the grandkids on the steps. A covered deck is $18,700 and a patio is $13,200, or $30,800 for both, including GST. You can add them now or later.

3. Site works: getting it onto your block

Transport, craning, footings, earthworks and service connections are quoted for your block. They depend on how far you are from Busselton, access for the truck and crane, your soil and land, your bushfire (BAL) rating and how far the power, water and sewer need to run.

As a guide, transport, craning, earthworks and service connections come to roughly $20,000 to $40,000 on most blocks. Farther or remote blocks, tight access or difficult ground can cost more. This is an early estimate only. Final costs depend on site access, soil and land conditions, BAL rating and service connections, and will be confirmed in a formal quote.

4. Who manages the site: owner-builder or registered builder

Peak builds the home. The site work is managed one of two ways.

As an owner-builder, which is usually the lowest total cost. In WA you need owner-builder approval for work over $20,000. It's for individuals (not companies or trusts) who own the land, intend to live on it when the work is done and have no immediate plan to rent or sell. You generally can't be an owner-builder again within six years, and if you sell within seven years you need home indemnity insurance. If the granny flat is for rental, check you're eligible before you apply.

With a registered builder, which many lenders ask for if you're using a bank loan. As a working estimate, allow around 20% of the total cost (the home plus site works) for the builder's fees. For The Ridge at $159,500 plus $20,000 to $40,000 of site works, that's roughly $36,000 to $40,000. Every builder prices differently, so ask yours for a quote, and talk to your lender or broker early.

5. Approvals

Every granny flat needs a building permit. In most residential zones, one up to 70 m² no longer needs planning approval if it meets the R-Codes. Rural lots follow your shire's own scheme. We explain it in our guide to WA granny flat rules.

6. How long it takes

Ten weeks in our factory from deposit to delivery. On the day, your home is craned into place in a morning, about half a day on your block. Footings and service connections are done separately, before and after.

Questions

Do your prices include GST?

Yes. Every home price on our website includes GST. We show the + GST figure underneath for anyone who needs it.

Are appliances and air conditioning included?

No. Kitchen appliances and air conditioning are quoted separately so you can choose your own.

Is the deck included in the price?

No. The home price is for the complete home. A covered deck is $18,700 and a patio $13,200, including GST, and every model page shows the prices with and without them.

How do I get a price for my block?

Tell us where your block is using the form on any page. We'll come back with the design that suits, its price and an early site estimate.

Sources

General information only, not legal or financial advice. Rules change and each shire applies its own scheme, so check with your shire before you build.

Let's talk about your block.

Tell us where it's going and what it's for. We'll come back with the design that suits, the price and an honest site estimate.

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Delivery day with one of our clients
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