Granny flats are often seen as a simple way to add another living space to your property.
In some cases, they are. but before you start choosing floor plans, room sizes or finishes, there is a more important question:
Can your property actually accommodate the granny flat you have in mind?
The answer often comes down to planning controls, site constraints, access, setbacks, flooding, existing buildings and the relationship between the new granny flat and your main house.
That is why we recommend checking the property first, before spending too much money on design.
What is a granny flat?
In planning terms, a granny flat is generally referred to as a “secondary dwelling”. It is a smaller dwelling that sits on the same property as the main house and remains subordinate to it.
A secondary dwelling is different from a dual occupancy, duplex or separate house lot. The distinction matters because different planning and building requirements can apply.
Queensland changed its rules in 2022 so secondary dwellings can now be rented to anyone, not just a family member. However, this change did not remove the need for relevant planning approval, building approval or other compliance requirements.
Do granny flats need Council approval in Brisbane?
Not always, but you should never assume a granny flat is automatically approved. Every new secondary dwelling requires building approval. Whether you also need a Development Application depends on the property, local planning controls and the proposed design.
In Brisbane, some properties are relatively straightforward. Others can be affected by planning controls that influence where and how you can build.
Before starting design work, it is worth checking:
- Your zoning
- Flooding or overland flow
- Character or heritage controls
- Neighbourhood plans
- Bushfire or environmental overlays
- Site slope
- Existing buildings and structures
- Available backyard area
- Side and rear setbacks
- Vehicle and pedestrian access
- Sewer and other infrastructure
Brisbane City Council also recommends checking the zoning and overlays affecting your property before starting residential building work.
The backyard size can be misleading
A large backyard does not necessarily mean you have a large buildable area.
For example, you may have plenty of grass but still need to work around:
- A sewer main
- Flood constraints
- Required setbacks
- Existing retaining walls
- Large trees
- Easements
- Significant slope
- Private open space requirements
- Access to the main dwelling
This is why a simple site review can save a lot of redesign later.
The goal should be to establish the realistic building envelope first, then design the granny flat to suit it.
Attached or detached?
A secondary dwelling can potentially be attached to the main house or constructed as a separate building. A detached granny flat is often preferred because it provides more privacy and separation between occupants. However, an attached design can sometimes make better use of a constrained property.
There is no single option that works for every site. The better approach depends on the existing house, available space, access, slope and planning controls.
One bedroom or two?
For most Brisbane properties, the design discussion usually starts with one or two bedrooms.
A one-bedroom granny flat can work well where:
- Backyard space is limited
- The dwelling is intended for one person or a couple
- Maintaining outdoor space is important
- Construction budget is limited
A two-bedroom layout may offer greater flexibility but requires more floor area and can have a larger impact on site cover, landscaping and the relationship with the existing house.
The aim should not simply be to fit the largest possible granny flat onto the site.
A smaller, well-planned design will often function better.
Think about privacy early
Privacy is one of the most overlooked parts of granny flat design. This applies both to the occupants of the granny flat and the people living in the main house.
Window placement, outdoor areas, entry points and orientation can make a substantial difference.
A good design should avoid situations where:
- Bedroom windows face directly into the main house
- The granny flat overlooks adjoining properties
- Both dwellings share the same small outdoor area
- Access requires people to walk past private parts of the main house
- The granny flat blocks natural light or ventilation to the existing dwelling
These issues are much easier to solve during concept design than after plans have been completed.
Do you need a survey?
Often, yes. A detail and contour survey gives your designer accurate information about the property, including existing buildings, ground levels and other visible site features.
Depending on the project, boundary information may also be required.
For simple sites, preliminary design work may sometimes start using available property information. For constrained sites, getting an accurate survey early can reduce the risk of designing something that later needs to move or change.
What about flooding and overland flow?
Flooding does not automatically prevent a granny flat from being built, but it can affect the design.
Depending on the property, you may need to consider:
- Minimum floor levels
- Building location
- Flood immunity
- Overland flow paths
- Structural requirements
- Access during flood events
This is one reason copying a standard granny flat plan from another property can cause problems.
The building needs to respond to your site.
Can you rent out a granny flat?
Yes, subject to the relevant approvals and requirements. Queensland removed the previous restrictions that generally limited secondary dwellings to household or family members. A lawful secondary dwelling can now potentially be rented to anyone.
However, owners still need to consider building approval, fire safety, tenancy requirements and any conditions attached to an existing development approval.
If you are specifically designing the granny flat as a rental, tell your designer and certifier early so the appropriate requirements can be considered.
Granny flat or dual occupancy?
This distinction is important. A secondary dwelling is intended to remain subordinate to the main dwelling.
A dual occupancy generally involves two dwellings that function as separate dwellings rather than one being secondary to the other.
The Queensland Government specifically distinguishes secondary dwellings from dual occupancies in its planning guidance.
If you are trying to create two substantial independent homes, separately title the dwellings or undertake a future subdivision, you may need to investigate a different planning pathway.
This should be worked out before the design progresses too far.
Start with the property, not the floor plan
After more than 15 years designing residential projects, one of the most useful things we can do for a granny flat project is identify the site constraints before the design becomes locked in.
At Designer Planning, every granny flat design package includes a free initial town planning review.
Our planning team can check the property and identify the main planning considerations before our building designers progress the concept.
This can help answer questions such as:
- Is a granny flat likely to be supported on the property?
- Are there planning overlays we need to design around?
- Is a Development Application likely?
- Is there an obvious location on the site that works better?
- Are there issues that should be investigated before spending further money?
Where possible, we would rather adjust the design early than prepare a full set of plans and identify a planning problem afterwards.
See the design before progressing
Once the site constraints are understood, the next step is developing a granny flat that suits the property and how you intend to use it.
Our concept designs include a 3D walkthrough so you can review the layout and spaces before moving further into documentation.
This is particularly useful for compact homes, where small changes to room sizes, storage, windows and circulation can make a large difference.
Granny flat design packages
Our granny flat plans start from $3,990.
This includes our initial design service, a 3D walkthrough and a free town planning review of your property.
Additional services such as surveying, engineering, certification or a Development Application may be required depending on the site.
If you are considering a granny flat, the best starting point is to send through your property address and a brief outline of what you want to build.
We can check the site first and identify any obvious planning issues before you commit to the design.