Brisbane has the most useful secondary dwelling rules in Australia. At 80 square metres of gross floor area — a third larger than the New South Wales and Victorian limits — and rentable to non-family members since late 2022, a Brisbane granny flat is not a studio at the back of the yard. It is a genuine two-bedroom home with its own income stream.
A related guide to consider while planning this work is Converting Part of Your House into a Granny Flat: Separation and Services.
For a homeowner with a reasonable block, this is one of the strongest returns available in Australian residential property: no land purchase, no stamp duty, and in many cases no development application.
The Rules
Size and siting
- Maximum gross floor area of 80 square metres in metropolitan Brisbane. Some rural areas permit up to 100 square metres.
- Non-habitable areas are generally excluded from that calculation — patios, carports and covered outdoor spaces. This is significant: a well-designed 80 square metre dwelling with a generous covered deck lives much larger than the number suggests.
- Rear setback of approximately 3 metres, and side setbacks of approximately 1.5 metres, subject to the applicable code.
- Minimum separation of about 1.8 metres between the secondary dwelling and existing structures, for fire separation.
- Total site coverage commonly capped at 50 per cent of the lot.
- It must be on the same lot as the principal dwelling and cannot be separately subdivided or sold.
Who can live in it
This is the key Queensland difference. Secondary dwellings in Brisbane can be rented to non-family members where the dwelling is compliant — a change enabled since late 2022. In New South Wales and Victoria the equivalent rules have historically been more restrictive in various ways, and the Queensland position gives Brisbane owners genuine flexibility.
Approval pathway
- Many compliant secondary dwellings proceed as accepted development, requiring no separate council planning application.
- A building approval from a private certifier is always required, regardless.
- Overlays still apply. A property affected by the Traditional Building Character Overlay, flood mapping, bushfire, landslide or biodiversity overlays will need more, and may require a development application.
The practical implication: check your overlays before anything else. Brisbane City Council’s online planning tools show every overlay on a property free of charge, and a FloodWise Property Report tells you the flood position. Those two checks determine whether your project takes three months or ten.
What It Costs to Build
Brisbane secondary dwelling costs run roughly $2,500 to $4,000-plus per square metre, with turnkey projects between $110,000 and $300,000-plus.
- One bedroom, 40 to 60 sqm — $150,000 to $220,000
- Two bedroom, 60 to 80 sqm — $180,000 to $280,000
- Custom builds and difficult sites — $250,000 to $300,000-plus
Site preparation, utilities and approvals add a further $3,000 to $15,000-plus, and considerably more on a sloping or constrained site.
Inside the build cost
- Site preparation, excavation and levelling — $6,000 to $30,000, and higher on Brisbane’s hilly inner suburbs
- Footings and slab, or stumps and subfloor — $18,000 to $45,000
- Frame, roof and external cladding — $40,000 to $80,000
- Windows, doors and shading — $9,000 to $22,000
- Plumbing, including sewer and water connection — $14,000 to $34,000
- Electrical — $8,000 to $20,000
- Kitchen — $11,000 to $26,000
- Bathroom and laundry — $16,000 to $30,000
- Internal linings, painting and flooring — $18,000 to $38,000
- Covered deck or patio — $12,000 to $35,000, and worth every dollar in this climate
- Driveway, path, fencing and landscaping — $7,000 to $28,000
- Termite management system — $2,000 to $6,000, and mandatory
Costs outside the build contract
- Private certifier building approval — $2,000 to $6,000
- Development application, where an overlay triggers one — $1,500 to $6,000 in fees plus $3,000 to $12,000 in consultants
- Design and documentation — $4,000 to $14,000
- Soil classification — $600 to $1,500
- Survey — $1,200 to $3,000
- Energy compliance assessment — $400 to $1,200
- Water and sewer connection — $2,000 to $9,000, considerably more where a main runs through the build zone
- Electrical supply upgrade — $1,500 to $12,000 where existing capacity is inadequate
- Stormwater and lawful point of discharge — $3,000 to $18,000
All in, a two-bedroom Brisbane secondary dwelling commonly totals $210,000 to $300,000. Turnkey quotes well under $150,000 generally exclude site costs, connections, driveways, landscaping and the covered outdoor area.
The Sewer and Stormwater Check
The most common expensive surprise. Water authority assets run through a great many Brisbane residential blocks, frequently diagonally across the rear yard where you want to build.
Before committing to a siting, obtain a sewer and water asset plan and overlay it on your survey. If a main runs through the build zone:
- Build over or adjacent under a build-over-asset approval, often requiring pier and beam footings bridging the main — add $8,000 to $25,000
- Divert the main — $20,000 to $60,000
- Move the dwelling — free, if you check early
Separately you need a lawful point of discharge for stormwater. On Brisbane’s sloping blocks this is often straightforward; on flat blocks where the land falls away from the street it can require a pump or on-site detention.
A related guide to consider while planning this work is Extending an Existing Granny Flat: Structure and Service Capacity.
Returns in the Brisbane Market
Brisbane rents for a well-finished two-bedroom secondary dwelling vary by location:
- Outer suburbs — Springfield, Forest Lake, Redlands, Logan fringe: $400 to $500 per week
- Middle ring — Chermside, Stafford, Mount Gravatt, Carindale, Wavell Heights: $470 to $600 per week
- Inner ring — where overlays allow it: $600 to $800 per week
A worked example
A two-bedroom, 75 square metre secondary dwelling in a middle-ring Brisbane suburb, built for $250,000 all in, renting at $530 per week:
- Gross annual rent — $27,560
- Gross yield on build cost — 11.0 per cent
- Less rates apportionment, insurance, maintenance, agent fees and vacancy at roughly 25 per cent — $20,670 net
- Net yield on build cost — 8.3 per cent
The 80 square metre allowance matters here. A Brisbane two-bedroom secondary dwelling can be a genuinely comfortable home rather than a compromise, which supports both the rent achievable and tenant retention — and in a market where good rentals are scarce, that is worth real money.
Effect on property value
Valuers typically attribute 50 to 80 per cent of build cost to the property’s value, depending on integration and how much yard was consumed. The return is mostly income rather than capital, which matters if you plan to sell within a few years.
Two design decisions affect valuation materially: whether the secondary dwelling has genuinely separate access, and whether the main house retains a usable private yard. On a 600 square metre Brisbane block both are achievable; on a 405 square metre inner-city block, one usually has to give.
Designing for the Subtropics
An 80 square metre dwelling in Brisbane’s climate can be genuinely pleasant if it is designed for the conditions rather than dropped on the block.
- A covered outdoor room. Excluded from the floor area calculation in most cases, and in Brisbane’s climate it becomes the most-used space in the dwelling. This is the single best design decision available.
- Cross-ventilation. Openings on opposite walls, positioned for the prevailing north-easterly summer breeze. A dwelling that can be cooled by opening two windows costs almost nothing to run.
- Ceiling fans in every room — $400 to $1,200 installed each and the best comfort return per dollar in this climate.
- Shading before glazing. Eaves, awnings and a verandah stop heat before it reaches the glass, and cost far less than high-performance windows.
- Ceiling insulation and a light roof colour. Roof heat gain is the dominant summer load.
- Roof space ventilation — eave intake and ridge exhaust.
- Raise the ceiling to 2,700mm. Small cost, large effect in a small dwelling, and it helps hot air stratify above head height.
- Kitchen and bathroom back to back to share a plumbing wall.
- Full-height storage designed in rather than added later.
- Sub-meter electricity and water to avoid every future dispute.
For family arrangements — an ageing parent or an adult child — build in accessibility from the start: step-free entry, wider doorways, a level shower, reinforced walls for future grab rails, and lever handles. These cost little to include and are expensive to retrofit.
Delivery Models
Specialist secondary dwelling builders offer standard designs with fixed pricing and a streamlined certifier process. Efficient on a flat, straightforward block. Read the inclusions carefully — site costs, connections, driveways, fencing, landscaping and the covered deck are frequently excluded.
Modular and prefabricated units are built off site and craned in. Shorter build time and minimal disruption, but craneage requires access, which many steep or narrow Brisbane blocks do not have. Total cost is usually comparable to conventional construction rather than cheaper.
Custom design and construct costs more and takes longer, and is the only realistic option on a sloping block, a character-overlay property, or a narrow inner-city lot where a standard design will not fit. On Brisbane’s hilly inner suburbs this is frequently the only path.
The Build-Under Alternative
Brisbane offers a second option that other cities do not: instead of a detached secondary dwelling, build in underneath an existing raised Queenslander.
Where the house already sits high enough — or can be raised within the 9.5 metre height limit while achieving the 2.4 metre minimum habitable ceiling — the lower level can accommodate a self-contained dwelling. Costs run $5,000 to $6,500 per square metre for the new level, which is higher per square metre than a detached build, but it consumes no yard at all and shares the existing footings, roof and services.
For a household on a small inner-city block where a detached 80 square metre dwelling simply will not fit alongside a usable yard, this is frequently the better answer. See our guide to renovating a Queenslander.
Tax Considerations
- Rental income is assessable and must be declared
- Expenses attributable to the dwelling, including depreciation on the new build, are generally deductible
- The main residence capital gains tax exemption may be partially lost for the period and proportion used to produce income
- Land tax may apply in some circumstances
- Formal family arrangements have specific CGT treatment worth advice on
Worth an accountant’s time before construction rather than after. The CGT consequence on a Brisbane property can exceed several years of rental income if handled without thought.
The Practical Sequence
- Check every overlay on the property through the council’s planning tools
- Obtain a FloodWise Property Report
- Order the sewer and water asset plan and check the build zone
- Commission a soil classification and a survey
- Confirm electrical supply capacity
- Obtain a lawful point of discharge for stormwater
- Appoint a private certifier and confirm the design complies before detailed documentation
- Verify the builder’s QBCC licence and confirm home warranty cover — compulsory above $3,300
- Get three fixed-price quotes on identical documentation with site costs itemised
- Hold a 15 per cent contingency
Brisbane’s combination of an 80 square metre allowance, exclusion of covered outdoor areas, unrestricted tenancy and an accepted-development pathway on many blocks makes this the most favourable secondary dwelling regime in the country. The projects that go wrong are the ones where somebody skipped the twenty minutes of overlay and asset checks at the start.
How Brisbane Compares to the Other Capitals
It is worth stating the comparison directly, because it explains why secondary dwellings are a stronger proposition here.
- Brisbane — 80 square metres gross floor area, covered outdoor areas generally excluded, rentable to non-family members, and many compliant projects proceed as accepted development with only a building approval required.
- Sydney — 60 square metres internal floor area, minimum 450 square metre lot for the complying development pathway.
- Melbourne — 60 square metres, must be all-electric, no planning permit needed in most residential zones under the small second dwelling reforms.
The extra 20 square metres matters more than it sounds. It is the difference between a compact two-bedroom unit and a genuinely comfortable one with a proper living area — which affects both the rent achievable and how long tenants stay. Combined with the exclusion of covered outdoor areas from the calculation, a well-designed Brisbane secondary dwelling can live like a small house.
The Covered Outdoor Area Advantage
Because patios, carports and covered outdoor spaces are generally excluded from the 80 square metre gross floor area calculation, the single best design decision available is a generous covered deck.
In Brisbane’s climate this is not a technicality — it is the most-used space in the dwelling for much of the year. A 20 square metre covered outdoor room attached to an 80 square metre dwelling produces something that functions as a 100 square metre home, at outdoor-room cost rather than enclosed-floor-area cost.
Design points worth getting right:
- Roof it properly with insulated panel and a lined ceiling rather than bare sheet
- A ceiling fan, weatherproof power and dimmable lighting
- Orient it to catch the north-easterly and shade the western afternoon
- Retractable blinds on the exposed side for storms
- Insect screening, so it is used at dusk
- A near-flush threshold from the internal living area
Cost: $12,000 to $35,000 within the overall build. It is the highest-return element of the entire project.
Verifying the Numbers Before You Commit
Three checks separate a project that works from one that does not, and all three are cheap.
- Overlay and flood status — free through the council’s planning tools and a FloodWise Property Report. A character or flood overlay converts an accepted-development project into a development application.
- Sewer and water asset location — a main running diagonally through the build zone costs $8,000 to $60,000 to work around, or nothing at all if you find out early enough to move the building.
- Site coverage and setbacks against the actual lot dimensions — the 50 per cent site coverage cap and the setback requirements together determine whether an 80 square metre dwelling plus a covered deck plus a usable yard actually fits. On a 600 square metre block it generally does; on a 405 square metre block it generally does not.
Under $2,000 in total, and together they answer whether the project is viable before any design money is spent.