An ancillary dwelling is a small, self-contained dwelling located on the same lot as another single house. It can be attached to the main house, integrated with the main house, or a separate building to the main house. Commonly known as a “granny flats,” ancillary dwellings usually have some facilities, such as a
small kitchen and bathroom, that allow occupants to live in them independently from the main house. Another option is the “Fonzie flat,”

Separate dwelling, which is the most common type we work with at Fox, but you can convert part of your existing home, as well as extend your existing home.

You need to understand the planning regulations that apply to ancillary dwellings in your local area. The Residential Design Codes set out the key planning regulations for ancillary dwellings, including minimum lot sizes, maximum floor area, and parking requirements.

A new ancillary dwelling will need building approval to ensure that it meets the safety (structural and fire), health, amenity, and sustainability requirements of the Building Code of Australia (BCA).

A granny flat can be defined as a fully self-contained home extension that is built on the same plot of land that the main home is. Essentially, it is another smaller home on your property. Usually, the granny flat is located to the rear of the main home, and it can share the backyard with the main home or have its own section of the yard fenced off. Local councils will dictate what the maximum size of a granny flat can be (usually no more than 70 square metres).

Click here to view our transportable granny flats.

Yes. A Building Permit is required to construct any dwelling, and council policies regarding constructing a granny flat vary. At Fox, we can assist/complete the process if you are unsure what questions to ask.

The journey from initial enquiry to move in day is very simple and straightforward, which means the hardest part is choosing which of our designs you like best. Once you’re happy with the design you’ve chosen, we’ll send you a quote and arrange a site visit if needed. We’ll also liaise with your local council on your behalf and manage all the paperwork. After that, part of the joy of working with Fox Granny Flats is our quick build times.

Due to the customisable nature of our designs, our granny flats can vary in price, starting from $79,990*. During the enquiry stage, we take the size, any inclusions or modifications to the design and location of transportation into consideration when producing your quote.

If you would like any further information on pricing, please contact our office on (08) 6117 5719. Alternatively, if you prefer you can email us at


We are a member of:

Our registration numbers are:

  • Building Contractor (BC): 103080
  • Builders Registration Number (BRN): 102022

Yes, Fox can take care of the entire project from design, approvals, manufacturing and installation of your granny flat.


We have a display village in Perth and we welcome you to visit and chat with one of our knowledgeable Fox sales and design consultants.

View our contact details

We have a range of sizes to suit your needs, starting at 20sqm, but we can customise to suit any specific design requirements.

See some of our designs here

We have a range of Fox Granny Flat designs that you can choose from and should you want to customise a design we will work with you to ensure you get your perfect home.

Our granny flats can be customised to suit your block and shape.

A granny flat is required to be separate from the house and be standalone. A building or structure that is attached to the house may be determined to be an extension of the primary dwelling, and therefore not a granny flat.

As a general guide, pre-construction can take a minimum of six months depending on how quickly relevant reports are received (four months if no planning is required), and construction & installation can take between 7-9 months. Please note these are estimated timeframes and are subject to a number of factors including suppliers and weather. 

Our base pricing in our Fox Granny Flats includes reverse cycle air conditioners to keep you cool in Summer and warm in Winter.

We have a range of standard colours for all our designs that you can choose from.

Yes! Our granny flats are relocatable, so they can be moved when you decide to move or sell on.
View our transportable granny flats here.

Fox offers options for the differently able, selections including wider doors are utilised throughout the to allow better access for those using walking frames or wheelchairs. For more information on your specific requirements contact our team.


Stud frame is a steel frame system with the studs typically 600mm apart, with cladding fixed to the outside of the frame, gyprock to the inside, with insulation fitted in between the studs. A steel roof trusses system is used to form the roof, with metal cladding attached externally.

The panel system is cool room panels; each panel has insulation foam with a thin layer of steel on the internal and external surfaces. Once installed, these panels are used for the wall and roof structure and are a finished product.

Our Fox team will run through all of your selection options during your pre start session and you can use any of our homes on display as inspiration.

Your dedicated Fox team will go through your plans and come up with a suitable plan for your home design – this means we look at your windows, shading, insulation options and control the temperature in the most natural way possible.

Your home will be built offsite in our factory in Gnangara. During this time, your land will remain untouched as we work on your home. Fewer materials are required while lowering the amount of waste we produce. We follow a system that enables most sites to avoid the need for excavation, including those properties located on a slope.

Additionally we offer a variety of options to our clients that support the health and sustainability of our planet. These options include the use of paints and stains with low VOCs, solar panels and hot water systems.

Solar panel installations are compatible with the majority of our granny flats. Our Fox team will be able to provide you with a solution that is best suited for your home, region and site orientation.

Energy ratings are measured using a star rating system from 0 through to 10 with a 6 star rating or equivalent required as a minimum. Computer software is used to model the home and takes into consideration things like the construction materials, the local climate, home orientation, its layout, colours and floor coverings.

Fox granny flats are built off-site, so there are no tradies at your property until the site works are carried out. They are constructed in a shorter time frame than traditional homes and because they are built in our factory, there are no delays with the weather or other external factors. Building a Fox Granny Flat gives you greater flexibility as they can be transported and installed practically anywhere, so if your circumstance changes you can relocate it with ease.

As proud Western Australian granny flat builders in Perth, we try to source all our materials from around Australia.


All new ancillary dwellings need building approvals. The team at Fox will help you obtain your building approval. Call us now and speak to one of our Fox reps, or pop into our display village.

You don’t need anything to start the conversation with our Fox team. Our Fox reps will talk you through the process and give you a good indication of what the next steps are for your project. Call us now and speak to one of our Fox reps, or pop into our display village.

Yes, we can amend your design, materials and inclusions to comply with the BAL report requirements.


Yes, we can do free site visits, but we encourage you to come into our showroom first to speak to one of our design consultants. This way, we can understand your needs better before the site visit occurs.

When looking to build one of our modular granny flats in Perth, you may require additional works to clear space and prepare the site. Works like this will typically be completed by external contractors that specialise in these areas. However, Fox can help arrange and assist with this.

When deciding how much space you’ll need for a granny flat, this will largely depend on the size you’re looking to build and whether it’s a 1 bedroom or 2-bedroom granny flat. Ideally, we would recommend at least 20sqm for the Granny Flat itself and allowing for a minimum 1m space from any boundaries. Note that different shires have different regulations on what your maximum size for the Granny Flat can be.

Your setback depends on your block and the relevant planning codes. Contact Fox, and we will help with your specific needs.

Given that we deliver modules across WA, delivery time will vary, but the majority of on-site installations are completed in a single day. For addition/extension modules and larger more complex projects, connections can take up to 2 weeks.

Following a soil test, an appropriate footing system will be designed for your site. Our standard footings system replaces the need for extensive earth moving or leveling equipment. The footing locations are determined by our plans and the pre-built modules are fastened to the footings. We consider the design closely to minimally affect any existing flora or fauna.

Transport costs are dependent on the distance of travel required and the size of the modules. An estimate is calculated early on at the preliminary price stage so that there are no surprises.

Crane hire is only applicable to projects with access issues and multiple storeys. For straightforward installations, crane hire can be around $5k while more complex deliveries where longer hire periods apply costs can be up to $10-$20k. Following a site investigation an estimate is provided at the preliminary price stage.

Let us know if you are in a cyclonic region, and we will build your Fox Granny Flat to comply.

We deliver our granny flats anywhere in WA.

The average install price is between $15k – $25k in the Perth metro area. This price will include all shire applications, engineering fees, elevations & relevant drawings, energy reports, site works & footings, and electrical & plumbing connections. This is only a guide and after we do your site visit, we can give you a firm installation price.

Yes. Specific site works may need to be undertaken or alternative footings used to allow for the slope. A site visit will determine the available options and the best course of action. If you require a site visit, we are more than happy to send one of our Construction Team members to assist you, whether you’re building a granny flat in Bunbury or Perth.


All Fox Granny Flats come with a 10-year structural warranty and a 6 month maintenance period.

The cost of each Fox project is simply the sum of the parts. Our standard inclusions form the basis of each project costing, upgrades can be made to nearly all internal items as well as heating and cooling, decking and external finish upgrades, which would all be priced separately.

Our aim is to ensure our clients know exactly what they’re getting and how much it will cost, with no surprises along the way.

Contact us for a quote

We’re happy to assist where we can. If securing finance is proving tricky, we can put you in touch with lenders who are more familiar with the prefabricated housing industry.

Want to learn more?

Reach out to our expert Fox Granny Flat team today.

Please note that our services are currently only available in Western Australia.