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Planning for a secondary dwelling

Understand the regulations regarding the construction of secondary dwellings (also known as granny flats or studios).

What is the relevant planning legislation for secondary dwellings?

The Standard Instrument LEP Order defines a secondary dwelling as “... a self-contained dwelling that: 

  • is established in conjunction with another dwelling (the principal dwelling), and 
  • is on the same lot of land (not being an individual lot in a strata plan or community title scheme) as the principal dwelling, and 
  • is located within, or is attached to, or is separate from, the principal dwelling”. 

The planning rules governing secondary dwellings are set out in the State Environmental Planning Policy (Affordable Rental Housing) 2009 (Affordable Rental Housing SEPP). This policy provides information regarding where a secondary dwelling can be built and the relevant design requirements that need to be complied with.

What residential zones can secondary dwellings be built in?

Secondary dwellings are permitted in most residential zones – including R1, R2, R3, R4 and R5. Schedule 1 of the Affordable Rental Housing SEPP provides detailed development standards for secondary dwellings. 

What is the maximum allowable floor area?

Generally the maximum floor area permitted will be 60m2. It’s important to note that the rules are determined by factors such the size of the residential block and the size of the existing house. Variations to these rules may be permitted by the local council subject to a development application being submitted. 

Can it be approved as complying development?

A secondary dwelling can be approved using complying development provided it complies with the requirements set out in the Affordable Rental Housing SEPP, including Clause 23. An accredited certifier can provide advice on the use of complying development to construct a secondary dwelling. The requirements of the Building Code of Australia (BCA) also will apply. 

Do I need to obtain a BASIX certificate for a secondary dwelling?

Yes, it’s necessary to obtain a BASIX certificate for a secondary dwelling when lodging a DA or CDC with the consent authority. Depending on the orientation of the development site and the design of the secondary dwelling, there may be unexpected costs involved to achieve the water, energy and thermal comfort targets in BASIX. 

It may also be necessary to investigate and consider a range of design options during the planning phase, including building materials, windows, floor and roof insulation and the type of hot water service to be installed. 

Is the payment of contributions required?

Some councils may require the payment of contributions for local infrastructure for secondary dwellings. It is important to determine what costs are involved early so that can be factored into the cost of the project. 

Although many councils have made a specific exemption for secondary dwellings, some councils will require contributions as high as $10,000. These levies will need to be paid before any construction work can begin. 

For more information about the planning requirements to build a secondary dwelling and the application process to be followed, go to the Department of Planning and Environment’s special information page.

To find out more, contact HIA’s Planning and Environment team.

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