How much does a granny flat cost in Perth?
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Perth's granny flat price list starts with a prefab unit, $80,000–$120,000 delivered to the block, and moves to $110,000–$160,000 for a one-bedroom flat built on site and finished ready to live in. The two-bedroom flat most people ask about is $140,000–$210,000, with $175,000 the usual figure, and the rate behind all of those numbers is $2,300–$3,500 per square metre built. Perth blocks lend themselves to this kind of build: 77.8% of the city's dwellings are separate houses (ABS 2021 Census), so there is usually a backyard to put one in. GST is included in every figure.
Comparing cities, or after the Australia-wide picture? See the national guide: How much does a granny flat cost in Australia?
Detailed Pricing — Granny Flat Cost in Perth 2026
| Service | Low | Typical | High |
|---|---|---|---|
| Prefab / modular granny flat — 1-bed (delivered) | $80,000total | $95,000 | $120,000 |
| Studio / 1-bed granny flat (35-45m², turnkey) | $110,000total | $130,000 | $160,000 |
| 2-bed granny flat (~60m², turnkey) | $140,000total | $175,000 | $210,000 |
| Custom / premium 2-bed (high-end finishes) | $210,000total | $260,000 | $320,000 |
| Two-storey granny flat (complete, incl. site costs + approvals) | $280,000total | $345,000 | $425,000 |
| Granny flat with attached single garage (complete, incl. site costs + approvals) | $170,000total | $210,000 | $260,000 |
| Garage / outbuilding conversion | $40,000total | $75,000 | $120,000 |
| Turnkey build (per m² built) | $2,300/sqm | $2,800 | $3,500 |
| Site works + service connections | $15,000total | $25,000 | $40,000 |
| Building permit + R-Codes assessment | $3,000total | $6,000 | $11,000 |
| Demolition / site clearing (if needed) | $3,000total | $6,000 | $15,000 |
| Driveway, path & basic landscaping | $5,000total | $10,000 | $20,000 |
| Privacy fencing (per m) | $80/m | $130 | $190 |
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Get Perth quotes →Prices include GST. Based on Perth metro area, October 2026. Outer suburbs may vary.
Perth’s Granny Flat Market in 2026
WA allows a granny flat (ancillary dwelling) of up to 70 m², for a relative, a friend or to rent out, and the 2024 R-Codes removed the old 350 m² minimum lot size. No planning approval is needed if it meets every deemed-to-comply standard, but a building permit from the council is still required.
It can’t be subdivided (strata, built-strata or green title), and only one is allowed per site. The table’s building permit and R-Codes row is $3,000–$11,000.
Prices by bedroom in the Perth table: one bedroom or a studio $110,000–$160,000, two bedrooms $140,000–$210,000, turnkey. At the 70 m² limit and the typical turnkey rate ($2,800 a square metre), a flat is about $196,000.
How Granny Flat Costs Vary Across Perth
Western Suburbs
Typical cost: $180k–$330k turnkey
Cottesloe, Claremont, Nedlands, Subiaco, Dalkeith. Perth’s most expensive area. Premium finishes to match high-value homes; budgets run to the top of the range.
Northern Coastal
Typical cost: $160k–$300k turnkey
Scarborough, Hillarys, Joondalup, Sorrento. Big coastal blocks suit detached 2-bed builds; sea-air sites benefit from corrosion-resistant detailing. Strong rental demand.
Southern Suburbs
Typical cost: $150k–$280k turnkey
Fremantle, Rockingham, Baldivis, Cockburn. A mix of heritage Fremantle lots and newer southern estates. Access and block type drive the price.
Eastern Suburbs
Typical cost: $120k–$230k turnkey
Midland, Guildford, Forrestfield, High Wycombe. More affordable, flatter blocks with easy access. Standard single-storey and prefab builds are the staple.
Hills & Outer
Typical cost: $120k–$230k turnkey
Kalamunda, Mundaring, Ellenbrook, Byford. Large blocks suit bigger builds; bushfire-prone hills areas need BAL-rated construction, which adds cost.
What You’ll Actually Pay — Common Perth Granny Flat Builds
Perth granny flats, each from the table.
1-bedroom granny flat — 40m², turnkey
$110,000–$160,000 total
The one-bedroom price: $130,000 typical turnkey, and anyone can live in it, a tenant included.
2-bedroom granny flat — 60m², turnkey
$140,000–$210,000 total
The two-bedroom price: $175,000 typical; with typical site works and connections ($25,000) it is $200,000.
Prefab / modular 2-bed — installed
$80,000–$120,000 delivered (1-bed row)
A delivered one-bedroom prefab is $80,000–$120,000 — the table’s only prefab row.
Garage / outbuilding conversion to studio
$40,000–$120,000 total
Garage conversion: $75,000 typical; a converted building must also stay within the 70 m² internal-area limit.
Custom architect 2-bed / two-storey
$210,000–$425,000 total
Custom two-bedroom $210,000–$320,000 or two storeys / over a garage $280,000–$425,000; one granny flat per site either way.
Granny flat prices in Perth (2026): 1 bedroom, 2 bedroom, prefab and turnkey
A granny flat in Perth costs $110,000–$160,000 for a 1-bedroom or studio of 35–45 m² built turnkey, with $130,000 typical, and $140,000–$210,000 for a 2-bedroom flat of around 60 m². Turnkey means designed, approved, built, connected and finished to move into. Per square metre built, that is $2,300–$3,500. A 1-bedroom prefab or modular flat is $80,000–$120,000 delivered, before the slab, services and finishing on site.
| Job | Low | Typical | High |
|---|---|---|---|
| Studio / 1-bed granny flat (35–45 m², turnkey) | $110,000 | $130,000 | $160,000 |
| 2-bed granny flat (~60 m², turnkey) | $140,000 | $175,000 | $210,000 |
| Prefab / modular granny flat, 1-bed (delivered) | $80,000 | $95,000 | $120,000 |
| Turnkey build (per m² built) | $2,300/m² | $2,800 | $3,500 |
| Site works + service connections | $15,000 | $25,000 | $40,000 |
| Garage / outbuilding conversion | $40,000 | $75,000 | $120,000 |
1 bedroom vs 2 bedroom granny flat prices in Perth: the second bedroom adds floor area, a longer roof and more wall, so the price moves with the square metres rather than the room count; the per-m² figure above is the way to compare two quotes of different sizes. What does not scale is the fixed cost: site works and service connections ($15,000–$40,000) are much the same for a 1-bed and a 2-bed, which is why the smaller flat is dearer per square metre.
Kit vs turnkey: a kit price is the building supplied, not built. Add the slab, the trades to erect and fit it out, the service connections and the approval before comparing it with a turnkey price. Converting an existing garage ($40,000–$120,000) is the cheapest route to a self-contained flat where the structure is sound.
What moves a granny flat quote in Perth:
- Size and layout: square metres set the build price; a bathroom and kitchen are the dearest rooms per metre.
- Site: sloping blocks, poor soil, tree removal and long runs to the sewer, water and power all sit in site works.
- Approval: Western Australian rules on size, setbacks and who can live in the flat decide whether it is a simple approval or a full application.
- Finish: standard fittings and finishes are the base; stone benchtops, premium tapware and timber floors move a build toward the custom band.
- Access: a tight side access limits machinery and prefab delivery, adding labour.
Ask every Perth builder for the same thing: a turnkey price, the square metres, and site works and approvals as separate lines, so the price list from each compares.
What Affects Granny Flat Costs in Perth
The 70 square metre line
WA calls a granny flat an ancillary dwelling, and the R-Codes allow one per site with a maximum internal floor area of 70 m²; the old minimum lot size has been removed (WA Planning). Our two-bedroom row sits comfortably inside that. A three-bedroom flat, which some locals search for, has to fit under the same ceiling, so it is drawn as a custom design and priced from $210,000–$320,000 rather than from a standard plan.
Two approvals, not one
An ancillary dwelling needs no planning approval when it meets every deemed-to-comply requirement, the 70 m² cap and your local scheme's setbacks included. What it always needs is a building permit from the local government, and the flat has to meet the National Construction Code (WA Planning). Budget $3,000–$11,000 for the permit and the R-Codes check, and expect a slower path if any setback has to be argued.
Prefab, turnkey or a conversion
The prefab row, $80,000–$120,000, is the unit landed on the block; the slab, the connections and the permit sit on top. The turnkey rows cover the finished flat but not the site. If a garage or outbuilding already stands on the block, converting it runs $40,000–$120,000, because the slab and the roof are already paid for. The two-storey row, $280,000–$425,000, is the one price here that includes site costs and approvals.
Sand, trenches and winter rain
Site works and connections are $15,000–$40,000, and the number climbs with the distance from the flat's wet areas to the house's sewer and power. Clearing an old shed or slab is $3,000–$15,000, a path and basic landscaping $5,000–$20,000, and a fence to give the tenant a yard $80–$190 a metre. Perth's rain is concentrated in June, July and August, with July the wettest at 147.0 mm and December the driest at 9.6 mm (BOM averages), so slabs pour faster in the dry half of the year.
Renting it out
Anyone can live in a WA ancillary dwelling, a relative, a friend or a tenant on a rental agreement, and the old family-only restriction is gone. It cannot be subdivided or strata-titled, so it stays on your title with the main house (WA Planning). Only 26.6% of Perth households rent, against 30.6% across Australia (ABS 2021 Census), which is part of why a self-contained flat in a suburb of separate houses finds a tenant.
Registered builder, insured build
Across most of WA, a job of $20,000 or more has to be done by a Building and Energy registered builder, and once residential work passes $20,000 that builder also arranges home indemnity insurance held in the owner's name, handing over the certificate before any deposit is asked for (Consumer Protection WA). Every turnkey row in our table crosses that line, so the registration number and the certificate are the first two things to ask for.
Heat, finishes and the garage option
Perth sits in NCC climate zone 5 and February averages a 31.7 °C maximum at Perth Metro (BOM averages), so insulation, shading and cooling belong in the quote rather than on a later invoice. Stone benches, premium floors and a deck are what carry a flat from the turnkey rows toward $210,000–$320,000. A flat with its own single garage, complete with site costs and approvals, is $170,000–$260,000.
How to Save Money on Granny Flat Cost in Perth
Frequently Asked Questions — Granny Flat Cost in Perth
Our Methodology
Our pricing comes from a mix of sources — public cost guides, tradie marketplaces, peak-body rate data, and individual builder sites — cross-referenced and then adjusted for regional cost differences. We produce these guides independently, and no tradesperson can buy their way onto the page or sway a figure. Every price is an estimate that will move with the details of your job, so we always recommend getting multiple written quotes. Last reviewed October 2026. Read our full methodology →