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How Big Can a Granny Flat be in NSW?

Are you considering adding a granny flat to an existing property? Whether you are planning this addition for family members or as a rental consideration, it is important that, together with all legal requirements, you also factor in how big a granny flat is allowed to be in NSW.

In today’s article, we take a look at what you need to consider when building a granny flat, as well as what the granny flat regulations for NSW are, and how you can make the most of the space that you are allowed to use for constructing your planned granny flat.

As a starting point, let’s do a quick recap of what the typical description of these dwellings are – and why they are not considered as primary dwelling but rather a secondary dwelling, the main house being referred to as the primary dwelling of the property.

What is a granny flat in NSW?

A granny flat, which is often referred to as a secondary dwelling, describes a self-contained dwelling that is located within, attached or separate to a larger home. Typically, the owner of the primary home will also be the owner of the granny flat as they cannot be sold separately (its one title)

Granny flats are often used by the elderly (although in most cases they are used for tenants). These structures have separate private entrances apart from the primary dwelling.

What certainly adds to their appeal, is that these units are also known for their affordability when it comes to property development.

What granny flat size is allowed?

The important thing to bear in mind when you are contemplating extending a property with a granny flat development, is that the options for size are not indefinite. You do not need Council approval to build your granny flat or Private Certifier Approval, provided you adhere to the minimum requirements as stipulated below.

In New South Wales, the allowed size for a granny flat is up to 60 square metres. This refers to the internal space of the granny flat, but there are also other considerations that you need to bear in mind.

If preferred, you can go smaller than this size – do take into account how it will be used, as smaller might not work in some cases where the person occupying the space needs more space.

Can I build a granny flat on vacant land?

According to granny flat regulations in NSW, you are required to have a minimum lot area of 450 square meters if you are planning to build a granny flat. Also important to know, is that you are only allowed to build one granny flat per property.

State Environmental Planning Policy guidelines also clearly state that there must be a primary dwelling on your property in order to get approval of a granny flat to be constructed. 

Am I allowed to build a double-storey granny flat on my property?

Provided that the height of this dwelling does not exceed 8.5 metres, and that you comply with the front and rear setbacks as laid out according to NSW legislation, a double-storey granny flat is possible – and can be an attractive option for creating a modern structure. However the distance required off the rear boundary to build a double storey granny flat is so substantial it only works in rare circumstances. 

The rear setbacks are typically 3 meters and the side setbacks are typically 0.9m. The setback from the main dwelling is 1.8m without the need for fire resistance design measures. 

Is a granny flat a separate dwelling then, or can I alter my home to create this space?

You are allowed to alter your current home to create a granny flat – which is good news if you want to save on funds and do not completely want to create a new structure from scratch.

However, you still need to comply with the law and need to ensure that your property is properly zoned residential to allow for a granny flat to become part of your property lot. The compliance hoops you will need to do to make this happen usually render this option non feasible.

Can I build a granny flat that is bigger than 60 square meters?

Although 60 square meters is the benchmark for most residential lots, some rural lots allow the secondary dwelling to be up to 80 percent of the main dwelling. However 60sqm is referred to as the livable space, you can add garages and large covered outdoor entertaining areas to the granny flat to make it much larger and functional

How can I optimally use the space of my granny flat?

Are you thinking that 60 square meters might be the small size for the development that you have in mind?

Consider this: Although you might be restricted in your internal space, there are still many steps that you can take to not only perfectly use the area that you have available, but also create great designs with some smart planning.

An important thing to note here, is to consider what the floor space of your granny flat includes. This could be your bedrooms, bathrooms, kitchen, dining room, living rooms and laundry room. These are the general areas that your granny flat would typically have and count towards the total internal space.

However, decks, garages, overhangs or sheds do not count as part of your internal space. Additionally, you can use roof cavities for extra storage, without needing extra space, and if you have a double-storey granny flat, you can even add a balcony to enhance the overall design.

Review the options that you have carefully, and you can make full use of your available space. Focus on both internal and external factors


Granny flats in NSW can be incredible investments that add value to any home. Always keep your allowed size for your property in mind, but do remember that these restrictions do not mean you cannot create beautiful spaces – it all comes down to planning and seeing the possibilities of what could be achieved!

If you are interested in adding a granny flat to your main property, do not hesitate to get in touch with us today – let’s work together to find the best solutions for your budget and the vision you have to make your dream granny flat a reality.