Adding a second dwelling to your property doesn’t automatically make it a ‘granny flat.’ In planning terms, there’s an important distinction between a secondary dwelling and a dual occupancy, and it affects what you can build, how big it can be, and whether you need a full Development Application.
Most clients call everything a granny flat when they first come to us. Here’s how to work out what you actually want, before you spend money on drawings for the wrong thing.
What is a secondary dwelling?
A secondary dwelling, the granny flat, is a residential use involving one dwelling for a single household, plus a smaller, subordinate dwelling and any outbuildings attached to either. It has to read as secondary to the main house, not as a second home in its own right.
- Usually capped by a maximum floor area, set by each council
- Doesn’t have to be occupied by family. A 2017 amendment to the Queensland Planning Regulation removed the rule that only related households could live in one
- Often accepted development if it meets council’s design requirements, meaning no Development Application needed
What is a dual occupancy?
A dual occupancy is two dwellings on one lot, or two dwellings on separate lots sharing common property, whether attached or detached. A duplex is the classic example. Each dwelling functions as its own home.
- Can generally be built at full size, without the caps that apply to a secondary dwelling
- Each dwelling can operate independently, with its own services and access
- More likely to need a Development Application, depending on zone and site
The simple test: could it stand on its own?
If you removed the main house, could the second dwelling still function on its own? Does it have its own laundry, services, parking, driveway and letterbox, or does it rely on the main house for some of those things?
- If it could stand alone, it’s most likely a dual occupancy.
- If it depends on the main house, it’s most likely a secondary dwelling.
Secondary dwelling vs dual occupancy:
| Check | Secondary Dwelling | Dual Occupancy |
|---|---|---|
| Relationship | Subordinate to main dwelling | Two separate dwellings |
| Size | Usually capped | Can be full size |
| Independence | Functionally tied to main dwelling | Each dwelling operates independently |
| Services/access | Often shared with main dwelling | Can be fully separate |
| Planning pathway | Often accepted development | More likely to need a DA |
| Occupants | No household relationship required | Separate households permitted |
| Design intent | Reads as ancillary | Can effectively operate as two homes |
Same rules across Brisbane, Gold Coast, Logan and Moreton Bay
The core definitions are worded the same way across most councils surrounding Brisbane, including Gold Coast, Logan and Moreton Bay. What differs between councils is the specific size limits and design requirements attached to a secondary dwelling, and the zones where a dual occupancy is triggered as assessable development. That’s where local advice matters.
Why getting this right matters
Design for the wrong category and you can end up with a floor plan that’s too big to qualify as a secondary dwelling, or a dual occupancy that’s been laid out like an accessory unit and won’t function as two genuinely independent, saleable or rentable homes. Either outcome means redrawing, delay, and extra fees you didn’t need to pay.
Get it checked before you commit to drawings
Our in-house town planner reviews your concept before it goes to working drawings, so you know which category you’re in, and what that means for size and approval, before you’ve spent money on a design that doesn’t fit.