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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 a secondary dwelling?

A secondary dwelling, or granny flat, is a self-contained home located within, attached to, or separate from another dwelling (the principal dwelling) on the same site. At no point can the secondary dwelling be subdivided from the principal dwelling.

The secondary dwelling continues to be a popular housing choice for different generations of the same family living together, by providing an independent and affordable housing option for elderly parents or young adults. The secondary dwelling can also provide a rental income stream for the owner of the principal dwelling, through short-term or longer-term lettings, subject to any necessary approvals.

NSW has led the nation in the number of secondary dwelling commencements, which reflects the favorable planning approval pathways available.

What are the approval pathways?

A council or accredited certifier can certify secondary dwellings as complying development in residential zones (R1, R2, R3, R4, and R5), without the need for a development application (DA). This is if the secondary dwelling meets specific development standards in the State Environmental Planning Policy (Housing) 2021 (Housing SEPP).

The planning provisions for secondary dwellings were recently transferred from the State Environmental Planning Policy (Affordable Rental Housing) 2009, to the Housing SEPP.

The Housing SEPP allows a new principal and secondary dwelling to be approved under a single complying development certificate (CDC). To be approved as complying development, the principal dwelling must meet the standards set out in the State Environmental Planning Policy (Exempt and Complying Development Codes) 2008 and the secondary dwelling must meet the requirements set out in the Housing SEPP.

If the secondary dwelling does not meet the requirements for complying development, a DA will need to be lodged with the relevant council. 

What are the Housing SEPP development controls?

Complying development under the Housing SEPP specifies that only the principal dwelling and secondary dwelling can be located on the lot and that the maximum floor area for the secondary dwelling is 60 sqm.

The minimum lot size for the construction of a principal dwelling and secondary dwelling is 450 sqm. If the land has an area less than 450 sqm, the development cannot be carried-out as complying development. However, an exception to this may be when a secondary dwelling is located entirely within the footprint of the existing dwelling house.

The Housing SEPP does not require any extra parking for the secondary dwelling. 

If the proposal does not satisfy all the requirements for complying development, there is the option to submit a DA for a secondary dwelling with the local council. 

Do I need to comply with BASIX?

Secondary dwellings need to comply with the requirements of the State Environmental Planning Policy (Building Sustainability Index: BASIX) 2004 as part of the approval process. This means that the secondary dwelling will need to achieve the water, energy and thermal comfort targets contained in the BASIX tool.

If the principal and secondary dwellings are to be approved as one development project, the BASIX certificate needs to cover both dwellings. 

Will the council require an infrastructure contribution?

Local councils may require the payment of a local infrastructure contribution for a DA approved secondary dwelling. This is if the council considers that the secondary dwelling will create an extra demand for public amenities and services.

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

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