What is the Average Granny Flat Size?

Granny flats (also known as mother-in law flats, in-law apartments and bonus units) have recently become a very popular addition to the Australian backyard. What’s the average size of a granny flat is a common question asked by homeowners looking to add a unit, or by homebuyers wanting to do their research on granny flats before buying a property.

The average size of a granny flat in Australia is between 50-60 square metres. Why is this? Well, this size dwelling allows for there to be enough space for a separate bedroom and living area. By creating this space you can build a granny flat that feels more like a small, freestanding home than a single room studio.

There is a lot of information to understand about granny flats, so read on to find out the average size of Australian granny flats, why to build one, the laws that surround them and the different layout options that you should consider when building.

The Average Granny Flat

In most cases, the average granny flat is comprised of one bedroom, a small living room, a kitchen and one bathroom. They are known for being small and compact dwellings – like a shrunken single storey house.

In Australia, its more common for the granny flat to be its own dwelling and not attached to the main residence. The flat is usually located near the rear boundary of the block, which allows for maximum square metre use and creating a space between the main house and granny flat as possible.

Keeping it under 60 square metres means that there will be no compliance issues from your state government or local council for the dwelling being too large. By creating a separate bedroom and living room, the flat will also be more appealing to potential tenants or as short-term, holiday letting accommodation such as Airbnb

The maximum size of a granny flat will really depend on where in Australia you are looking to build. This is also the case with the rules and regulations surrounding whether you can rent out the flat to someone who isn’t in your immediate family, or use it as holiday accommodation.

Why Build a Granny Flat?

Granny flats give you flexibility. These buildings serve as extra accommodation, so they have a multiple of uses. They are perfect as a teenagers retreat, self-contained unit for the parents or can be great to rent out short or long term to supplement your income. A granny flat can also serve as a home office, art studio, or music room.

Before you can break ground on the build you must also consider obtaining building approval. Factors that can impact obtaining building approval include the size of the block, the shape of the block, zoning regulations and where underground utilities are located. This research should be done well in advance of starting the build.

Granny Flat Size in New South Wales

In NSW, the maximum size of a granny flat is 60 square metres, with the block of land being at least 450 square metres in size. The land also has to have a street frontage of at least 12 square metres. NSW is one of the best states for granny flat regulations because you can rent them out to tenants just like a normal house.

Granny Flat Size in Western Australia

WA has similar laws, with granny flats being legal to build in all residential zones, under the conditions that more than one main home and one granny flat exist on the property. The size of the granny flat itself also can be no lager that 60 square metres. Like NSW, WA homeowners are also allowed to rent out granny flats if they choose to.

Granny Flat Size in Tasmania

Tasmanian granny flat rules vary from council to council as there is no statewide policy. In Hobart, there no set maximum square footage, but the maximum area is based on the percentage of the floor area of the main home. For example, if the main house is 200 square metres, the granny flat can be 30% of this (which is 60 square metres). You are also allowed to rent out your granny flat in Tasmania.

Granny Flat Size in The Northern Territory

If you are in the Northern Territory, there is a size limit to 50 square feet for residential areas and the dwelling will need separate electric, water and sewer lines. Renting out the granny flat is legal.

Granny Flat Size in Queensland

For QLD granny flats, the rules vary from council to council. If you are in Brisbane the size of the granny flat can be up to 80 square metres if the block of land is at least 600 square metres. For the Gold Coast the rules are a little more complicated. The flat must be smaller than half the main house, along with sharing a common driveway, sewer and water supplies.

Granny Flat Size in ACT

In the ACT there were regulation changes in 2013, so you no longer need a family member to live in the granny flat. The block size must be 500m2 or larger and the granny flat size must be in between 40m2 and 90m2. The size of the house plus the granny flat must comply with the plot ratio that is allowed for the block.

Granny Flat Size in Victoria

VIC has tougher restrictions. Currently only an immediate family member is allowed to live in one. If they leave the flat has to be removed. This means that you can’t privately rent out the flat or have non-family occupy the dwelling.

Granny Flat Size in South Australia

For SA residents there are even more restraints. Granny flats can’t exceed 60 square metres or 70% of the existing dwelling size, whichever is less. The granny flat also has to be attached to the main dwelling and the block needs to have 100 square metres in outdoor space. Like in VIC, only immediate family can reside in granny flats; they cannot be rented out.

Layout Options

One of the great things about building a granny flat are the numerous different layout options and building materials that you can choose from. A lot of the time granny flats are built to look like smaller versions of the main house, but there are no hard and fast rules that mean you have to comply with this.

If you are wanting to experiment or try out some different layouts, a granny flat is a great way to do this. Maybe you always wanted to add a loft bed or a walk in shower? The 60 square metre limit may be small, but it is still big enough to have nice features. The standard layout of a granny flat usually has one bedroom so that there is a decent sized living area and bathroom. If you are willing to make the living area, bathroom and kitchen a tad more compact it is possible to squeeze in a second bedroom, which could add even more value to the dwelling if you are planning on renting it out.

Having outdoor living space is also important in granny flat builds. By adding a patio or deck to the building you will increase the space of the flat without breaking any laws. Just because a granny flat is small doesn’t mean that you shouldn’t enjoy kicking back on the deck on a summer afternoon!

Building Design

Interior design trends change over time, but keeping having open plan living to maximise square foot usage will always be a wise move when living in smaller spaces. If you expect guests in the flat a new trend is to add a murphy bed for additional sleeping needs. These beds fold up against the wall, so when they aren’t in use they take up hardly any space in the flat.

For the shell of the building, you can’t go wrong with the classic concrete slab and timber frame, but there are other options out there. Over the last few years kit granny flat homes have started to gain traction. They are a cheap option, but you need to do your research before buying one.

Wanting to save some money on your build? Look into using reclaimed materials. Shipping containers have recently become a popular choice as granny flat structures as they are readily available and quite cheap to buy. You will still have to have them fitted out, and if using second containers, be aware of what has been transported inside them.

Another popular design is building a stick frame flat but cladding it secondhand corrugated iron. This gives the building a very “Australian” centric feel and can add some old school charm to an otherwise new building.

Now you know the average size of granny flats in Australia, the state laws surrounding them and some of different design layouts to choose from there’s only one more thing to do. Find a builder and make the dream a reality!

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