Granny flats

Secondary dwellings, commonly known as granny flats, can be a positive way to add value and flexibility to your home.

Granny flat

What is a secondary dwelling?

A secondary dwelling or granny flat is a self-contained dwelling on the same lot of land as the principal dwelling (not being an individual lot in a strata plan or community title scheme). A secondary dwelling may be constructed in the following forms:

  • Attached to the principal dwelling
  • Detached from the principal dwelling
  • Separate dwelling within the principal dwelling

What is the maximum size of a secondary dwelling?

Sixty square metres. It must also meet requirements on height, building setbacks, maximum site coverage and maximum floor area.


Are secondary dwellings permissible in rural zones?

Yes. Refer to section 2.2.7 of the Hornsby DCP for requirements for secondary dwellings on rural allotments.


Are secondary dwellings permissible in residential zones?

Yes. Refer to the State Environmental Planning Policy (Affordable Rental Housing).


Can I subdivide a secondary dwelling?

No. Secondary dwellings must remain on the same title as the principal dwelling and can only be sold together.


Does a Section 94 levy apply?

Yes. Section 94 Development Contributions apply to all new secondary dwellings, including alterations and additions to an existing dwelling to create a secondary dwelling.


Do Building Code of Australia (BCA) requirements apply?

Yes. All relevant requirements within the BCA apply. Some secondary dwellings may change the building classification under the BCA.


Where can I find the requirements for a secondary dwelling?

These are available from the NSW Department of Planning and Infrastructure website. The design requirements for secondary dwellings in rural areas can be found in the Rural chapter of the Hornsby Development Control Plan.


How do I apply for approval to build a secondary dwelling?

There are two ways to apply for approval:

Complying development in residential zones

If your plans for a secondary dwelling satisfy all the provisions of the Affordable Rental Housing State Environmental Planning Policy (SEPP) 2009 and the requirements of the Exempt and Complying Development Codes SEPP 2008 you can apply to have the development approved by a Council-accredited certifier or private accredited certifier.

Development application

If your proposal is in a rural zone or does not meet all the requirements under the Affordable Rental Housing SEPP 2009 and the Exempt and Complying Development Codes SEPP 2008, you will need to lodge a Development Application with Council. The secondary dwelling will be required to meet the requirements of the Hornsby Local Environmental Plan 2013.