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What is an ancillary dwelling?

An Ancillary Dwelling is a self-contained dwelling on the same lot as a single house which may be attached to, integrated with or detached from a single house, as defined by the Residential Design Codes (R codes). As a minimum, to be considered self-contained, an ancillary dwelling must include a kitchen.

What are the main rules?

Ancillary dwellings are:

• Limited to 70m2 of internal habitable floor area; or
• May be increased to 80m2 of habitable floor area, where the ancillary dwelling has been designed for accessibility (Pursuant to cl. 5.5.2 – C2.3 i, ii, iii, iv | R codes)

i. External and internal doors provide a minimum 820mm clear opening;

ii. Internal corridors to be a minimum of 1200mm in corridors with openings on side walls;

iii. A visitable toilet preferably located within a bathroom; and

iv. Toilet and toilet approach doors shall have a minimum 250mm nib wall on the door handle side of the door and provision for the installation of grab rails.

• Limited to one (1) on any freehold or Strata lot.

(The Shire of Mundaring does not have the discretion to approve floor areas above 80m2).

In addition to the above, Ancillary Dwellings:

• Should be constructed in a style, colour and material that is complementary to the main residence, particularly if the site is on the Shire’s Local Heritage List / Survey;
• Should be located in as close proximity to the main residence as reasonably practicable, having regards to the need for privacy of both residences;
• Are provided with at least one on site car parking space;
• Are no longer restricted to be occupied by family members of the main
• Are subject to compliance with Local Planning Scheme 4 and the R codes if located in the Residential Zone.
• May be subject to
• an assessment against the bushfire regulations (refer to section/s below); and
• an environmental assessment (refer to section/s below)

Planning approval is not required where an Ancillary Dwelling is compliant with the R codes and/or Local Planning Scheme No.4, and not located in a special control area (such as a bushfire prone area), or on a heritage lot. Specific properties can be discussed with Planning Officers to determine the relevant approval pathway.

Bushfire

As a majority of residential and rural land in the Shire is mapped as bushfire prone, most proposed Ancillary Dwellings will require planning approval. An applicant will need to engage a Bushfire Practitioner (level 2/3 consultant) to undertake a Bushfire Attack Level Assessment (BAL) and prepare a Bushfire Management Statement (BMS). These documents will need to be provided with the application for planning approval. An Ancillary Dwelling subject to BAL-40/FZ may not be supported by the Shire.

Environment

Where a lot is mapped as local natural area (LNA) or contains native vegetation or a watercourse that may be impacted as a result of development, the applicant/landowner should engage the Shire to undertake an Environment Asset Inspection. It is best practice for the Environment Asset Inspection to occur at the same time as the Bushfire Practitioner is undertaking their bushfire attack level assessment.

Ancillary Dwellings should be located in already cleared areas or degraded areas and in close proximity to the main residence to allow for overlapping asset protection zones and thereby reducing the level of vegetation modification required.

The Shire may not support a development where the impact on the environment is considered unacceptable.

Effluent Disposal

In some cases, an ancillary dwelling may be able to connect to the existing effluent disposal system for the main house. If this is not possible, a second system may need to be installed. An application for a second effluent disposal system is still made to the Shire but will be referred to the Department of Health for approval.

 You can contact the Shire’s Health Service on 9290 6742 for more information about wastewater systems.

Building Permit

A separate building permit application will need to be submitted to the Shire’s Building Services for approval prior to construction and after planning approval is issued. The application for the building permit will require structural details and engineering certification. Some planning conditions may need to be met before the building permit can lodged and/or issued.

You can contact the Shire’s Building Service on 9290 6660 for more information about wastewater systems.

Apply for planning approval and building permit

More information and contact

For more information about planning approval, contact Planning Services on (08) 9290 6740.

For more information about building permits, contact the Building Services on (08) 9290 6666

Useful Links:

• Design Guidelines 
• Development in Bushfire Prone Area
• Local Planning Strategy and Scheme