Granny Flats

If you’ve been searching “how much does a granny flat cost,” you’ve probably noticed the answer varies wildly depending on who you ask. Between builder quotes, council fees, and site works, it’s hard to know what a realistic granny flat cost in Perth actually looks like.

This guide breaks down starting prices for granny flats WA homeowners can expect in 2026, what drives the cost of a granny flat up or down, and how to budget for the additional costs.

Granny Flat Cost Perth: The Starting Price

The starting base price includes the structure and standard fittings, excluding site specific works. As a general guide, here’s what you can expect to pay for a Summit Granny Flat in Perth, based on our current designs:

Granny Flat Size Starting Price
1-bedroom granny flat From $171,218
2-bedroom granny flat From $183,555
3-bedroom granny flat From $196,689

 

These figures cover the base build only — finishes and site works are additional and are priced on top of these amounts. View the base prices of our granny flat range, here.

Two Costs Added on Top of the Base Price

Finishes

The level of finish you choose — tapware, flooring, cabinetry, tiling — has a real impact on your final number. As a rule of thumb, allow:

  • 50sqm granny flats: approximately $15,000 for finishes to include floor coverings to main living areas/kitchen, carpets to bedrooms, window treatments, internal wall painting, air conditioning.
  • 70sqm granny flats: approximately $20,000 for finishes to include floor coverings to main living areas/kitchen, carpets to bedrooms, window treatments, internal wall painting, air conditioning.

This budget lets you move beyond the base spec into finishes that feel more like a full home than a basic add-on. Please note the above prices are estimates, and dependent on your project scope.

Site Works

Site works are the part of your granny flat cost that’s hardest to standardise, because every block is different. Slope, soil conditions, access for trucks and machinery, existing services (power, water, sewer connections), and retaining requirements all factor in. As site works are priced specific to each site once we’ve assessed your block — they aren’t included in any standard prices.

This is usually the biggest source of “surprise” costs in granny flat builds generally, so getting a proper site assessment upfront is the best way to avoid budget blowouts later.

What Affects Your Final Granny Flat Price in WA?

A few things typically move a granny flat quote up or down from the base price:

  • Floor size — increasing the floor size of designs changes both the build cost and your finishes allowance
  • Site conditions — sloped blocks, rock, or difficult access increase site works
  • Council requirements — some shires have additional conditions that affect design or approval costs
  • Finish level — standard vs upgraded fixtures, flooring, and cabinetry
  • Connections — distance to existing power, water, and sewer points

Getting an Accurate Quote

If you’re in Perth and weighing up a granny flat, the best next step is getting your block assessed so you’re working with real figures, not just a starting price.

Ready to find out what your granny flat will actually cost? Get in touch with the Summit team for a site assessment and quote.

Speak to our team