A Complete Guide To Building Granny Flats


  • Author Tony Gronowski
  • Published March 16, 2024
  • Word count 698

This guide provides you the background, and what you need to know, to prepare for building a granny flat so you can make the right decisions and have a stress-free build.


There are a number of standard regulations associated with granny flats – although it’s always a good idea to check with your local authorities before proceeding, just in case there are local variations.

Granny flats are traditionally a secondary dwelling on the same block of land as the main home. They are not separately titled or subdivided and can be attached to the main home or detached.

Most regulations will allow a maximum of one granny flat to be built on a site, along with one main home.

You do not have to provide additional parking for the granny flat.

Lots must be at least 450 sqm, and a minimum of 12m-wide frontage.

The floor area should be a maximum of 60 sqm, although attached garages, workshops, storage rooms, patios or carports are not included in this calculation.

Can be a fast tracked complying development approval if designed to the relevant building code.

Garages, sheds etc can be converted to granny flats, but must be inspected by a structural engineer, who can issue a structural engineer’s certificate certifying that the slab and framework is built to Australian building standards.

A granny flat must be built at least 900mm off the side boundaries to be a complying development. If it is inside 900mm (or 1.5m if your block is larger than 900sqm) on the side boundaries it must have a fire-rated wall and will have to get development approval.

Rear setback must be at least three metres (or five metres if your block is larger than 900sqm.

A granny flat must be built at least 1.8m from existing structures such as sheds, carports or houses, unless the wall is fire-rated.

Setbacks are subject to change depending on the slope of the land and building height.

A two-storey granny flat or addition over a garage is possible but may require larger setbacks from the boundaries.


With the right design you can create a fantastic granny flat home to live in!

Since there is a maximum of 60 sqm to work with, you need to use it wisely. We suggest minimising the hallway area to maximise the living space. An L-shape design can do this in a way that provides a minimal hallway and still separates the bedrooms/bathroom from the living spaces.

An attached alfresco area will transform your granny flat into an entertaining space. Bifold or stacked doors can provide a seamless transition from kitchen/living to the outdoor space to maximise the entertaining area.

An island bench in a kitchen can create a larger space by doubling as a meals area.

Keep privacy in mind when designing your granny flat so as to not detract appeal from either the main house or granny flat. A private space will be much more appealing to live in and easier to rent, and a separate private entrance is the best way to keep it private.

Selecting a Builder:

Make sure they are a licensed builder and have had no previous disputes. You can check a builders’ license and history by doing a license check on the NSW Fair Trading website.

When checking over quotes, it’s important to clarify what they have included in the price. Very cheap quotes might only cover the bare minimum to seem lower than the competition and you could then be hit with all the extras that were not included, such as an additional cost to run mains power more than 10m or floor coverings.


Make sure the quote is detailed and itemised to show exactly what you are getting; if it is not then there will be conflict between you and your chosen builder on what or how much was included.

Thoroughly read through the entire quote and if you’re not sure of something ask the builder on receiving the quote, rather than after the job has started.

Ask for references from previous clients they have worked with to see how they were to deal with and how the quality of build was.

This article is proudly presented by Sydney Home Extension Co.



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