If you’re thinking about a granny flat in Brisbane, the first thing to get straight is what Brisbane City Council actually calls it. There’s no “granny flat” category in the City Plan. What you’re building is a secondary dwelling, and that one word decides almost everything about how easy or hard your project is going to be.
Get the secondary dwelling rules right and you can often build without lodging a development application at all. Get them wrong and you’re straight into a full DA, public notification, and a much longer timeline. Here’s what actually applies under Brisbane City Plan 2014.
What counts as a secondary dwelling
Under City Plan, a dwelling house can include two dwellings: the primary house, and a secondary dwelling. A secondary dwelling has to be smaller and clearly subordinate to the main house, it can’t be separately titled, and it’s meant to function as one household unit with the main dwelling, even if a different household lives in it day to day.
That last point matters. A secondary dwelling is not the same thing as dual occupancy. Dual occupancy is two genuinely separate dwellings on one lot, assessed differently and held to a different code. If your granny flat tips over the secondary dwelling thresholds, it gets treated as dual occupancy, and that’s a different, more involved approval pathway.
The size limit: 80m²
For most residential lots in Brisbane, a secondary dwelling can be up to 80m² gross floor area. On rural residential lots the cap lifts to 100m². Gross floor area is measured around the outside of the walls and generally excludes uncovered decks and patios, so an 80m² footprint usually gives you a bit more livable space than the number suggests once you account for wall thickness.
Go over the cap and you’re no longer looking at a secondary dwelling under the accepted pathway. You’re into DA territory.
Where it has to sit
Two site rules decide whether your design stays in the accepted development lane:
- Proximity to the main house. The secondary dwelling generally needs to be attached to the primary dwelling or located within 20 metres of it. This is part of what makes it read as “one household” rather than two separate homes.
- Separation for fire and amenity. Where the secondary dwelling is detached, current provisions call for a minimum separation from the primary building, generally around 2 metres, to satisfy fire separation requirements under the National Construction Code and avoid poor outcomes on light and access between the two buildings.
Setbacks and site cover
Setbacks depend on your lot size and what’s already established on the street:
- Larger lots (over 450m² standard, or over 600m² for rear lots) generally need a 6m front setback for a secondary dwelling.
- On smaller lots, the setback usually matches whatever the neighbouring house is set back, down to a minimum of around 3m.
- Side and rear setbacks are typically in the 1.5m to 3m range depending on which code applies to your lot (standard Dwelling House Code or the Small Lot Code).
- Overall site cover, all structures combined, generally needs to stay under 50% of the site area.
Height is also capped in the front setback area: the front 5 metres of the site is generally limited to single storey, in keeping with the size of structure the Queensland Development Code has traditionally allowed there.
These numbers move around depending on your specific lot size, frontage, and which neighbourhood plan or overlay applies, so treat them as a planning starting point, not a final answer. This is exactly the kind of detail we check against your lot before you commit to a design.
What every secondary dwelling needs regardless of size
Whether it’s 40m² or the full 80m², a secondary dwelling intended as a self-contained unit needs its own cooking facilities and its own bathroom. It also shares the primary dwelling’s street address and, in most cases, its refuse collection arrangements, since it isn’t a separately titled property.
Parking is one area where the rules have been shifting. Older guidance points to needing at least one additional car space for the secondary dwelling. More recent state-level provisions for secondary dwellings move toward not requiring extra car parking beyond what’s already provided for the primary dwelling, on the basis that a secondary dwelling shouldn’t need parking on top of the main house’s allocation. Because this is an area actively being updated, confirm the current position for your specific site before you lock in a design that assumes either position.
Can you actually rent it out?
Yes. Since 2022, Queensland removed the requirement that only family members could live in a secondary dwelling, and that change has stayed in place, giving homeowners the freedom to rent a compliant secondary dwelling to anyone. This is the single biggest reason granny flats have become a serious rental income play in Brisbane rather than just a family living solution. Rules can still shift at a state level, so if rental income is the whole point of the build, it’s worth a quick confirmation of the current position before you commit, particularly if your project is going to take a while to get through design and construction.
What pushes you into a full DA
You’ll need to lodge a development application, rather than proceed as accepted development, if any of the following apply:
- The secondary dwelling is bigger than the 80m² (or 100m²) cap
- It sits more than 20 metres from the primary dwelling
- Your property falls under an overlay that removes accepted development status regardless of size, most commonly the Heritage overlay, Traditional building character overlay, or Wetlands overlay
- You’re actually proposing dual occupancy rather than a true secondary dwelling
- Your lot sits in a zone where secondary dwellings aren’t accepted development at all
Character and pre-1946 areas are the ones that catch people out most often. If your existing house was built before 1947 and sits in a Traditional building character overlay, removing or altering part of it, even to make way for a secondary dwelling, can trigger the need for planning approval on its own, separate to the secondary dwelling question.
Flood-prone and overland flow areas add another layer. A secondary dwelling on a flood-affected lot may need to be elevated, which changes both the design and the assessment pathway.
Accepted development doesn’t mean no approval at all
This is where people get tripped up. “Accepted development” means you don’t need a development application or planning approval from Council before you start. It does not mean you can skip approval altogether. You still need:
- A self-assessment against the Dwelling House Code, or the Small Lot Code if your property qualifies as a small lot, plus any relevant zone or neighbourhood plan codes
- Building approval from a licensed private building certifier, confirming the design meets the National Construction Code
Every secondary dwelling in Queensland needs building approval regardless of whether it needed a planning approval. The two approvals are separate, and skipping the certifier step isn’t optional just because Council didn’t need to see the plans first.
How to check your specific lot
Before you get attached to a design, run your property through Brisbane City Council’s City Plan Interactive Mapping. You’re looking for three things:
- Zone. Confirms whether secondary dwellings are accepted development on your lot at all.
- Overlays. Heritage, Traditional building character, Flood, Wetlands, and others can each add requirements or remove accepted development status outright.
- Neighbourhood plan. Some neighbourhood plans set their own variations on setbacks, height, or size that sit on top of the general City Plan rules.
The practical takeaway
Most standard residential lots in Brisbane can carry an 80m² secondary dwelling through accepted development, without a DA, provided you’re clear of overlays and the design meets the Dwelling House Code. The moment you’re in a character area, a flood zone, chasing something bigger than 80m², or genuinely building a second separate dwelling rather than a subordinate one, the project shifts into DA territory and the timeline and cost both move with it.
That’s the split worth knowing before you spend money on a design: is this a straightforward accepted development secondary dwelling, or does your lot’s zone, overlay, or your own brief actually point toward a DA. Getting that assessment right at the start is what keeps a granny flat project on budget and on schedule.