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Can You Build a Granny Flat on a Duplex?

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If you have a duplex, you may wonder – can you build a granny flat on a duplex?


Unfortunately no. Both duplexes and granny flats are considered by the Council to be dual occupancy. This means that you can only have one, not both, on your property. To explain further, a granny flat is a “secondary” dwelling. As such, you are not allowed to put this secondary dwelling on a plot of land that already has more than one dwelling on there.


Today I will cover if you can find ways around this regulation, such as whether it is possible to find any alternative means to having three dwellings on the one 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 using AirBnB to rent out your granny flat as well as a room in your main home. I will talk about why Council has this regulation and why they do not like you having more than two dwellings on one property.


living together

Most people don’t want many people living under one roof. So read on to see how this can be avoided


Lastly, I will discuss what zones in New South Wales (for instance) may let you have multiple dwellings on your property…


Are There Ways Around This Duplex Rule?


You may be able to find ways around this, but it all does depend on your property.


As mentioned, a granny flat can generally not be built on a duplex, as on your Torrens title (that is, the person who is named as the owner of the land) there are already two dwellings. As such, adding in a third dwelling probably will not work.


However, if you subdivide your duplex, which will split your Torrens title, you will now only have “one dwelling” on the title. You may now have found a loophole, and given yourself an opportunity to build a granny flat on your duplex.


This will depend upon how your duplex is set up, if there is enough room on your land, and if your local Councils’ regulations allow it.


It is probably pushing the boundaries slightly, so I definitely recommend that you check with your local Council as to what you can build on the new lot.


Alternative Means of Having Three (3) Dwellings on One (1) Property. Is it Possible?


An alternative means to seeing if you can have three dwellings on your property is seeing if it is possible to get your property rezoned.


You can see what zones in New South Wales allow three dwellings underneath the sub-heading “What Zoning in NSW May Allow Multiple Dwellings on Your Property” below.


This article discusses the benefits of rezoning your property, what it can cost, and how you can go about getting it done.


Using AirBnB to Rent Out Your Granny Flat and a Room in Your House


Share housing is a common way of renting a room in a house these days – generally, the people that live in the house will have their own bedroom, while they jointly enjoy with one another the remainder of the premises.


So, it is possible to use AirBnB to rent out both your main home as share housing, and also rent out the granny flat.


What I suggest is that you cordon off one section of your primary dwelling, and rent this out on AirBnB through short term rentals. This way, you can keep the rest of the primary dwelling for yourself.


rent sign

You will have to decide if renting any part of your property will work for you


Then, you can also rent out the granny flat.


This does make it legally possible to have “three dwellings” on the one property, and you can use them for whatever reason you find is necessary – such as to make an income, or for the additional room for people to reside.


It is important to note that, in regards to making an income from the granny flat, this is as long as your state allows you to rent out the granny flat for a source of income. Every state has their own rules when it comes to this.


In New South Wales, you have no issues, you can rent out the granny flat for whatever price you like, as you can rent it to unrelated tenants.


Western Australia, the Australian Capital Territory, Tasmania and the Northern Territory will also all let you gain rental income from a granny flat.


However, in Victoria, a granny flat is called a Dependant Person’s Unit (for short, a DPU). The tenant must be dependant on the person/s in the primary dwelling (for example, they might be a parent, a grandparent, or a teenage child).


In South Australia, a granny flat is called Dependant Accommodation. The occupant must be an immediate family member of someone that lives in the main home.


In Queensland, the rules vary between Councils’. Some Councils’ may let you rent it out to non-family members, others may not.


Plus there are capital gain tax implications that you need to be aware of as well.


Why Don’t Council Like This?


Though you may have found a loophole for getting multiple dwellings on your property, it is important to note that it is something that Councils very much dislike!


One reason is that the Council sees multiple development projects risky. These risks include:


  • Over-Population in an area – Councils have issues with many people living on one property. These ‘risks’ include traffic concerns, waste-water concerns and fire safety concerns. Effectively when many people live in one space, if can overflow into greater problems and safety concerns for neighbouring people as well.


  • Finance – Many people have bitten off more they can chew when planning a development, scraping together just enough cash to get Council approval, and but then not having enough funds to complete the construction.

As such, it’s important that you set yourself a budget from the start. You can see exactly what it cost me when I built my granny flat here.

You should also learn how to negotiate with your builder and tradies, which you can read about here.


  • Dealing with difficulties that may arise – Small issues may come up when building your granny flat, which can slow down the time it takes to finish. For example, if you experience rainy weather during your project, you may have to stop work for a few weeks.

It may also take you longer to get your application approved by Council than you think. So, it may help to hire a professional, such as a drafter or architect to help you with your plans.

It’s important to keep in mind that problems may arise that may set you back, and you won’t generate a profit until the project is complete.


  • Tax implications – It’s important to keep in mind that you will have to pay tax on building materials, your rental income, and also a Capital Gains Tax. If you do not take this into account you may overestimate the profits you will get from your build.


Essentially, Councils’ like to see maximum return for the minimum risk, so to successfully obtain permission to develop multiple dwellings on one property, first you must understand the risks involved, and then work on reducing, or even eliminating them.

Other than that, you must also look at your property size, and ensure that you can meet all Councils’ regulations, including that you can:



What Zoning in NSW May Allow Multiple Dwellings on Your Property?


The various property zones in NSW that may permit multiple dwellings on the East Coast include the below residential zones*:


  • R2 – This allows for various types of housing, such as bed and breakfast (B&B) accommodation, dual occupancies, and multi-dwelling houses (i.e. villas and townhouses).
  • R3 – This zone allows for townhouses, villas, and residential flats.
  • R4 – This permits residential flats.
  • R5 – This provides for inner city units and serviced apartments.


Basically’ the number after the “R” indicates the maximum dwellings which might be allowed with the right council concent; R2 = 2 dwellings, R3 = 3 dwellings etc…


The below rural zone may also permit multiple dwellings:


  • RU4 – This permits bed and breakfast accommodation.


It is important to note that this does depend upon your Council. For example, Newcastle tends to allow these multiple dwellings, but Gosford does not. Blacktown will not permit multiple building in the R2 zones, only in the R3 and R4.


As such, I strongly suggest that you contact your Council for their input before proceeding.

*This zoning was correct at the time of writing, but may have changed Again, I recommend contacting your local Council for their advice.




It is a standard, nationwide regulation that you can only have either a granny flat or duplex on your block of land, not both. This is as they are both considered to be dwellings, and you can only have two dwellings on your property.


However, I hope this post has helped you find some loopholes for building up to three dwellings on your block of land if that is what you wish.


But if you want more information on whether you should choose to build a granny flat or a duplex, you can see where I have written, “Granny Flat vs. Dual Occupancy” – Find Out What You Should Do”. This post discusses the advantages and disadvantages of both, which may help you decide what you should do.


However, if you have made your decision and you are ready to start building your own granny flat, click here to find out how to DIY,your very own granny flat.