What our analysis shows
Analysis by Granny Flat Numbers, data as of 23 October 2026
- A standard two-bedroom 60 m² flat on a flat metro block costs $187k in South Australia and $238k in the Australian Capital Territory, turnkey. Sydney sits at $220k.
- The finish you choose moves the price more than anything else: $87k between budget and premium on the same 60 m² flat. A steep block adds $33k; the approval route adds only $8k.
- Shrinking the flat saves less than people expect. Going from 60 to 40 m² removes a third of the floor area but only 24% of the cost, because the kitchen, bathroom and connections stay the same. Per m², a 40 m² flat costs $4,180 against $3,670.
- Factory-built does not mean cheap. Once transport and a crane are paid, a prefab module came out within $3k of a site-built flat in our model.
- Rent covers the build fastest on the Gold Coast (8.4 years after tax) and slowest in Wyndham (15.2 years), using government bond data for 2-bedroom rents.
Turnkey cost of a 60 m² two-bedroom flat by state, cheapest first
- South Australia$187,000
- Tasmania$193,000
- Queensland$198,500
- Western Australia$198,500
- Victoria$199,000
- New South Wales$220,000
- Australian Capital Territory$237,500
Standard finish, flat block, services within 12 m, fast-track approval, metro build rates, incl. GST.
What moves the price most
We changed one thing at a time on a Sydney reference flat ($220,000) and measured the effect. The list is in order of how much each choice moves the final number.
| Change from the reference flat | Effect on the total |
|---|---|
| Premium instead of budget finish | +$87,000 |
| Owner-builder kit instead of a builder | −$68,500 |
| 80 m² instead of 60 m² | +$60,000 |
| 40 m² instead of 60 m² | −$53,000 |
| Steep block instead of a flat one | +$33,000 |
| Regional NSW instead of Sydney | −$32,500 |
| Sewer 40 m away instead of 12 m | +$10,000 |
| DA instead of a CDC | +$7,500 |
| Prefab module instead of site-built | −$2,500 |
Two of these are in your hands before you call a builder: the finish level and the floor area. The block and the distance to the sewer are fixed by the site, which is why two neighbours can get quotes $40,000 apart for the same plan. Our guide to site costs and connections breaks those down.
Cost by state and size
The same model at three sizes. A 40 m² flat is usually a studio or one bedroom, 60 m² fits two bedrooms, and 80 m² is allowed in Victoria's planning rules from 15 October 2026 and in several Queensland councils.
| State | 40 m² | 60 m² | 80 m² | 60 m², regional |
|---|---|---|---|---|
| New South Wales | $167,000 | $220,000 | $280,000 | $187,500 |
| Victoria | $151,000 | $199,000 | $253,500 | $169,500 |
| Queensland | $151,000 | $198,500 | $252,500 | $169,500 |
| Western Australia | $150,500 | $198,500 | $253,000 | $169,000 |
| South Australia | $142,000 | $187,000 | $238,000 | $159,500 |
| Tasmania | $146,500 | $193,000 | $245,500 | $164,500 |
| Australian Capital Territory | $178,500 | $237,500 | $305,000 | $201,500 |
Size caps differ: NSW allows 60 m² (more only where the council's LEP says so), South Australia and Western Australia 70 m², the ACT 90 m². An 80 m² flat in NSW needs a development application under a council control that allows it. See the rules in each state.
How each line is worked out
Construction. A rate per m² for each finish level ($2,450, $3,000 and $3,900 in Sydney), adjusted for the state, for regional areas (18% lower) and for small flats, where the premium rises to 12% at 30 m².
Site preparation. Excavation, levelling and the slab base: $12,000 on a flat block, $25,000 with some slope or tight access, $45,000 with rock or retaining walls.
Connections. Sewer, water, power and stormwater run from the main house: $10,000 when the flat is within 12 m, plus $350 for each extra metre of trench.
Design and approval. Drawings, engineering and the energy report ($8,000), then the state's approval route. Council contributions are added where they apply, such as section 7.11 charges in NSW.
What is not included: demolition of an old shed or garage, removing large trees, bushfire-rated construction (BAL-29 and above) and furniture. The methodology page lists every input and where it comes from.
What it can earn
We matched each build cost to the median rent for new bonds in the same area. On a 60 m² two-bedroom flat, these areas returned the build cost fastest:
| Area | Build cost | 2-bed rent / week | Net yield | Payback |
|---|---|---|---|---|
| Gold Coast (QLD) | $198,500 | $750 | 16.2% | 8.4 yrs |
| Cairns (QLD) | $169,500 | $600 | 14.9% | 9.0 yrs |
| City of Melbourne (VIC) | $199,000 | $678 | 14.4% | 9.3 yrs |
| Newcastle (NSW) | $187,500 | $640 | 14.4% | 9.3 yrs |
| Eastern Adelaide (SA) | $187,000 | $628 | 14.2% | 9.5 yrs |
This week's worked example
Week of 19 October 2026. A new example, rule and owner report every Monday.
A 70 m² two-bedroom flat with a standard finish on a block with some slope, services 20 m from the house, in Townsville: our model puts it at $207,500 turnkey ($182,500–$232,000), or $2,960 per m². At the area's median 2-bedroom bond rent of $520 a week it would return 10.3% net and pay back in 12.7 years after tax.
Rule check: Tasmania's draft SPP amendment 01/2026 proposes lifting the secondary residence limit from 60 to 90 m²; it was on exhibition from 10 June to 22 July 2026.
From an owner (VIC, 2021): A design for a self-contained unit failed the building code because it used the kitchen sink as the laundry tub: the code requires a kitchen sink, a laundry tub and a basin as separate fixtures.
Payback is after agent fees, insurance, maintenance and tax at 30%, with no loan. Run your own numbers in the rental yield calculator, or see rents in all 42 areas.