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Granny Flat WA Regulations – Guidelines Revealed

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When planning on building a granny flat in WA, you must know your regulations. But don’t let this deter you, here are the rules for Granny Flats in WA:


You must have a minimum property size of 450sqm (unless your local Council states differently). The maximum floor area your granny flat is allowed is 70sqm. Although this may differ across local Councils up to 100sqm. this is likely to be more flexible in rural areas. And it is possible to rent out your granny flat to non-family members, but approval from your local Council is typically required first.


Today I will cover how to build a granny flat on your Western Australian property.

DON'T PAY A FORTUNE FOR YOUR GRANNY FLAT. Find out how to deal with council and build a granny flat for the lowest cost possible. Learn More.


I will discuss what it costs to build a granny flat in WA and other important rules that must be obeyed.


Before finalising your build in Western Australia be sure to follow the rules below


I will talk about the rules for granny flats in the City of Stirling, the Cockburn Council, and the City of Wanneroo, so you can see the differences between Councils’. Finally, I will give you a list of granny flat builders in WA.


Update March 2024


We have great news for you all in Western Australia. In 2024, the Cook Government in WA announced the planning reform changes that are coming to relax the amendments and restrictions that were previously placed upon building granny flats, in a hope to boost housing supply all across the state.


The revised State Planning Policy 7.3 was bought out in mid-March 2024, and is due to become into effect by mid-April this same year.


The new regulations? I have listed these for you below:


  • When previously a minimum lot size of 450 square metres was needed, granny flats can now be built on blocks smaller than these, as long as they do not exceed 70sqm.
  • Granny flats that are no bigger than 70 square metres will no longer need planning approval from Councils, as long as they meet the Councils setback regulations.
  • An extra parking bay will no longer be a requirement, unless they are a long distance from public transport (a ‘long distance’ is one where a car is most likely to be required due to this distance).


Why are these changes being made, you may wonder? They are to make the planning process easier for both owners, builders, and Councils. By getting rid of the requirement for planning approval, difficulties in the administrative industry will be reduced, and so the time it takes to start building a granny flat should be lessened a lot, which will allow for quicker construction. This should also make additional living space available, which will also assist with the chronic housing crisis that is current across the state.


And by getting rid of the parking bay requirements, this opens up much more space for either the dwelling or privacy, such as a garden.


Yes, really, it has all been put in place to help. The Government wants you to have that secondary dwelling that you would also like to have on your property.


You can see quotes straight from the mouth of our planning Minister that confirms what I just said above here.


So, you will no longer have the burden of gaining planning approval. What will your responsibilities be then?


Your small second dwelling will still need the below:


  • Any necessary building permits. This means that whilst you may no longer need a permit to utilise your own land for building (that is, the planning permit), you must still follow all regulations for construction and design.
  • To meet the criteria in the Building Code of Australia.
  • To convene to the R-Codes (residential design code) setback and location rules.


This is a good thing, that your same construction requirements will still apply – it ensures that all quality and safety standards stay in place.


You can also not subdivide the land once a granny flat has been built upon it, or sell the granny flat singly – that is, it can only be sold together with your main home.


I do also strongly suggest that you check with your local Council as to their exact requirements around granny flats – these may include size, conditions for privacy, and other rules. I recommend this as all Councils do have different guidelines to which you may abide by, which you will see when I discuss the City of Stirling or the Cockburn Council below.


Can You Build a Granny Flat on Your WA Property?


WA’s granny flats regulations run under the Planning and Development Act 2015, and are fairly lenient compared to other states. For the most up-to-date and recent, detailed information in regards to building a secondary dwelling in WA, you can see the Australian Planning Commission’s website here.


Similar rules apply in some circumstances:


  • Only one granny flat can be built on each lot
  • If you build a granny flat, you are not allowed to subdivide your lot (unless it is allowed under the local planning scheme)
  • No minimum lot size is required, as long as your granny flat is no larger than 70sqm, and as long as you meet all setback requirements in the r-Codes (unless your local Council states otherwise).


So, if planning on building a granny flat, you need to understand the regulations that apply to your area, including:


  • Minimum lot size
  • Maximum floor area
  • Parking requirements


The Residential Design Codes shows the key regulations, but these can vary between Councils’.


As such, I recommend that you call your local Council, and ask to speak to the planning department. While speaking to them, find out the exact regulations that apply to your area. As each suburb or local council can have different rules.


You should also speak to the building approvals department, and find out:


  • Their approvals process
  • What you need to be aware of to gain approval
  • What information they require to approve building plans.


I suggest you ask for all this information in writing.


Your Council can also provide you with other information, including;

  • Additional garbage bins


Changes that were made under the State Planning Policy 3.1 (SPP 3.1 – prepared under section 26 of the Planning and Development Act 2005) also must be looked into. Until these changes were made, planning regulations only allowed;


  • A direct family member of the main home to live in the secondary ancillary dwelling.


However, the changes have made it possible to rent granny flats to non-family members.


They can now be used to provide housing for:


  • Private tenants
  • Carers
  • Unrelated seniors
  • Students


There are no restrictions on how many people can live in the secondary dwelling, so they can house:


  • A single person
  • Couples
  • A small family.


Please note that:


  • The changes do not automatically apply
  • Approval from your local Council is typically required before your granny flat can be occupied by a non-family member.


Costs to Build a Granny Flat in Western Australia


The average cost of building a granny flat in WA is $120 000.


But this price can change very quickly.


Factors to consider are:


  • Size – While granny flats are typically small spaces, they are not all that way. If you have the space, you can have 3-4 bedrooms.

However, these will cost more as they take more time and use more materials.

The average cost for a 1-bedroom granny flat ranges from $50 000 – $100 000.

Add more rooms, add more money.

  • Design – Granny flats have both standard and custom-made designs. You’ll spend more on something custom-made.
  • Additional tasks – Quotes are based around things such as easy access to a site.

The price will rise if the area needs to be prepared prior to building the granny flat.

This can be anything from excavation to clearing obstructions (i.e. trees).

  • Rates – When you talk to your Council, ask if your granny flat will impact your rates.

Your rates are determined on the rental value of your property, so may increase.

  • Fees – When you talk to your Council, ask what the fees (i.e. permits) are for your granny flat.

You need to be aware of additional charges ahead of building, so you can budget for them.

  • Servicing – You may need to install new sub-meters for electricity, gas, and water, depending if you plan to rent out the granny flat.

Contact gas and electricity distributors, and the Water Corporation.

Discover what options are available and decide which suit you best.

  • Installation fees – You are also likely to need a licensed plumber or electrician to install the new services.


If you find the costs of a granny flat in WA too high for your budget, it is possible to reduce the price.


Things you can do include:

  • Keep it basic – Just standard fittings can save you up to $10 000.
  • Do the construction yourself – The average price a tradie is paid is $50/hr. Save by choosing to DIY.

See my article “Can You Build Your Own Granny Flat?” for advice on how to do just that.


What is the Maximum Granny Flat Size in WA?


SPP 7.3 limits granny flats to a maximum floor area of 70sqm.


However, this may differ across local Councils’.


City of Stirling Granny Flat Rules


As with other areas in WA, the minimum lot size required for a granny flat in the City of Stirling once was 450sqm, and if your lot was less than 450sqm you may not have been allowed to construct a granny flat. However this will all change come mid-April 2024.


You are limited to a maximum floor area of 70sqm. Setbacks are dependent on boundary wall length and height – see Table 2A and 2B of the R-Codes to determine setbacks.


The City of Stirling requires written consent for anyone other than family members of the main home to occupy the granny flat. There also must be no common property between the titles (i.e. you cannot build on a strata-titled lot).


However, regulations that differ are:


  • Any other items such as landscaping, retaining walls or decking require separate approval
  • The number of car parks required depends on the distance from a train station or high frequency bus route. If within 800m from a train station or 250m from a high frequency bus route, no parking is needed. If outside of these distances, one car space at the granny flat must be provided.


*Please note – I got this information from the City of Stirling’s website and it is subject to change.


For latest information, visit their website.


Cockburn Council Granny Flat Rules


Again, the minimum lot size required in the Cockburn Council is 450sqm, but this too will change come mid-April 2024.


Regulations that differ include:


  • Car parks required is conditional on far it is to a train station (800m) or a high frequency bus route (250m). If the distance is greater than this, then a car spot at the granny flat is necessary.
  • Residential and resource zoned areas may be allowed a floorspace of 70sqm – 100sqm. 100sqm is the liveable area only, so does not include verandahs, patios, decks, carports/garages, etc.
  • Approval is required for the granny flat to be located anywhere than behind the main building line
  • The design, materials and colours of the granny flat shall match or suit those of the main home
  • The use of second-hand materials is not allowed.
  • Proposed granny flats on lots bigger than 1100sqm or with a high bushfire rating have additional requirements.


*Please note – This information was gathered from the City of Cockburn’s website and is subject to change.


For the latest information, see their website.


List of Granny Flat Builders in WA


Below is a list of builders of granny flats in WA;




The regulations for a granny flat in WA have always been quite lenient in comparison to other states.


You must:


  • Have a maximum lot size of 450sqm, until the new regulations are introduced in mid-April 2024 (unless your local Council states otherwise)
  • Build your granny flat to a maximum floor area of 70sqm (again, some Councils’ state differently, up to 100sqm)
  • Get approval from your local Council if you wish to rent out your granny flat to a non-family member.


The average cost of building a granny flat in WA is $120 000, though it is possible to lower this. Now you are armed full of knowledge, happy building!