Western Australia · Planning guide
Granny flat rules in WA
In Western Australia a granny flat is called an ancillary dwelling and it is governed by the Residential Design Codes Volume 1 (the R-Codes). The R-Codes set a deemed-to-comply pathway for an ancillary dwelling on the same site as a single house or grouped dwelling, with a maximum internal floor area of 70m2 and a requirement that it sits behind the street setback line. If the design meets every deemed-to-comply provision and the lot is not heritage-protected, the Planning and Development (Local Planning Schemes) Regulations 2015 remove the need for development approval, although a building permit is still required. Council instruments can modify some of these provisions, so the answer depends on the address.
Sources read on 9 September 2026. Provisions are quoted word for word from the instrument.
What counts as a granny flat in WA
The R-Codes do not use the words granny flat. The instrument that applies across the whole state is the Residential Design Codes Volume 1, made under Part 3A of the Planning and Development Act 2005. It defines an ancillary dwelling as a self-contained dwelling on the same site as another dwelling, and it allows the ancillary dwelling to be attached, integrated or detached.
That definition matters because it sets the scope of the rules. A self-contained unit with its own kitchen and bathroom on the same lot as your house is an ancillary dwelling. A second full house on its own strata lot is not, it is a grouped dwelling and it is dealt with under the dual occupancy rules instead.
ANCILLARY DWELLING - self-contained dwelling on the same site as a dwelling which may be attached to, integrated with or detached from the dwelling.
Read the source · retrieved 9 September 2026
The R-Codes applies to all residential development throughout Western Australia. The R-Codes are divided into two volumes (refer Table 1.4a). R-Codes Volume 1 applies to all single house and grouped dwelling developments; and multiple dwelling development in areas coded R10-R60. R-Codes Volume 2 applies to multiple dwelling (apartment) developments in areas coded R80 and above and R-AC.
Read the source · retrieved 9 September 2026
The deemed-to-comply rules for an ancillary dwelling
Part B clause 5.5.1 of the R-Codes sets out the deemed-to-comply requirements for an ancillary dwelling on a lot coded R40 or below. The unit must be associated with a single house or grouped dwelling on the same site, it must have a maximum internal floor area of 70m2, it must provide parking under clause 5.3.3, and it must be located behind the street setback line.
Two further tests are easy to miss. The ancillary dwelling must not stop the main house from meeting its own minimum open space and outdoor living area. And the ancillary dwelling must comply with all the other R-Code provisions that apply to single houses and grouped dwellings, except the site area rule in Part D, the street surveillance rule in most cases, and the outdoor living area rule.
That last exception is important for small lots. Because Part D site area does not apply to an ancillary dwelling, you do not need the extra site area that a second grouped dwelling would need. The density code on your lot does not stop you building a granny flat, as long as the house and the flat together still meet setbacks, open space, privacy and overshadowing rules.
Ancillary dwelling associated with a single house or grouped dwelling and on the same site where: i. C1i deleted by amendment dated 10 April 2024; ii. there is a maximum internal floor area of 70m2; iii. parking is provided in accordance with clause 5.3.3 C3.1; iv. ancillary dwelling is located behind the street setback line; v. C1v deleted by amendment dated 10 April 2024; vi. ancillary dwelling does not preclude the single house or grouped dwelling from meeting the required minimum open space and outdoor living area; and vii. ancillary dwelling complies with all other R-Code provisions, only as they apply to single houses and grouped dwellings, with the exception of clauses: a. Part D, 1.1 Site area; b. 5.2.3 Street surveillance (except where located on a lot with secondary street or right-of-way access); and c. 5.3.1 Outdoor living areas.
Read the source · retrieved 9 September 2026
Ancillary dwelling is of a small scale and designed to support people living independently or semi-dependently to the residents of the single house or grouped dwelling, sharing some site facilities and services.
Read the source · retrieved 9 September 2026
Higher density codes: Part C
If your lot is a single house coded R50 or above, or a grouped dwelling coded R30 or above, Part C of the R-Codes applies instead of Part B. Part C has its own ancillary dwelling element, clause 2.8, with the same 70m2 maximum internal floor area and a limit of one ancillary dwelling per site for single houses and grouped dwellings.
Under Part C the ancillary dwelling must not stop the primary dwelling from meeting its maximum site cover and its minimum private open space, soft landscaping, trees and deep soil area. The R-Codes also say that site cover, lot boundary setbacks and solar access for adjoining sites are assessed for the ancillary dwelling and the primary dwelling together, so the combined footprint is what counts.
Note: The above provisions relate to the ancillary dwelling portion of the development, with the exception of 3.1 Site cover, 3.4 Lot boundary setbacks and 3.9 Solar access for adjoining sites which would need to be assessed in combination with the primary dwelling. The primary dwelling would still need to comply with all relevant provisions of the R-Codes.
Read the source · retrieved 9 September 2026
The size of an ancillary dwelling allows for adequate internal amenity whilst remaining incidental to the primary dwelling.
Read the source · retrieved 9 September 2026
Part B includes provisions applicable to single houses in areas coded R40 and below, grouped dwellings and multiple dwellings (including the dwelling component of mixed use development) in areas coded R25 and below. Part C includes provisions applicable to single houses in areas coded R50 and above, R100-SL and R-AC, grouped dwellings in areas coded R30 and above, R100-SL and R-AC; and multiple dwellings (including the dwelling component of mixed use development) in areas coded R30 to R60 inclusive.
Read the source · retrieved 9 September 2026
Do you need development approval for a granny flat?
Often not. Schedule 2 of the Planning and Development (Local Planning Schemes) Regulations 2015 contains the deemed provisions that sit inside every local planning scheme. Clause 61 lists works that do not need development approval, and item 7 of the table covers an ancillary dwelling on the same lot as a single house or grouped dwelling.
The exemption has three conditions. The R-Codes must apply to the works, the works must comply with the deemed-to-comply provisions of the R-Codes, and the works must not be located in a heritage-protected place. If any one of those fails, for example because the flat is larger than 70m2 or sits forward of the street setback line, you must lodge a development application and the council will assess it against the design principles.
Development approval and a building permit are different things. Even when the planning exemption applies, the Building Act 2011 still requires a building permit before building work starts. The R-Codes flowchart makes the same point by sending exempt single houses straight to the building permit stage.
The erection or installation of, or alterations or additions to, any of the following on the same lot as a single house or a grouped dwelling — (a) an ancillary dwelling; (b) an outbuilding; (c) an external fixture; (d) a boundary wall or fence; (e) a patio; (f) a pergola; (g) a verandah; (h) a deck; (i) a garage; (j) a carport. (a) The R-Codes apply to the works. (b) The works comply with the deemed-to-comply provisions of the R-Codes. (c) The works are not located in a heritage-protected place.
Read the source · retrieved 9 September 2026
A person must not commence or carry out any works on, or use, land in the Scheme area unless — (a) the person has obtained the development approval of the local government under Part 8; or (b) development approval is not required for the development under clause 61.
Read the source · retrieved 9 September 2026
A person must not do building work unless — (a) a building permit is in effect for the building work; or (b) a building permit is not required for the building work under Part 5 or regulations or an order mentioned in Part 5 Division 1; or (c) the work is done in accordance with a building order; or (d) the work is done in the course of taking action under section 118(2).
Read the source · retrieved 9 September 2026
What your council can change
The R-Codes are a state instrument, but Part A clause 3 lets local planning frameworks amend, replace or augment the deemed-to-comply provisions. A local planning scheme can amend, replace, augment or exclude any R-Codes provision as the Regulations allow. Local planning policies and local development plans can modify a listed set of provisions without WAPC approval, and any other provision with WAPC approval.
For a granny flat the practical effect is that the street setback, lot boundary setback, building height, garage setback, fencing and outbuilding provisions your flat must meet may have been varied by your council. The 70m2 floor area cap in clause 5.5.1 is not on the list of provisions a policy can change without WAPC approval, so a council that wants a different cap needs the Commission to agree.
Local planning frameworks may amend, replace and/or augment the deemed-to-comply provisions of the R-Codes Volume 1. Schemes may include clauses that amend, replace, augment and/or exclude any provision of the R-Codes as provided for in the Regulations.
Read the source · retrieved 9 September 2026
For the purposes of this Scheme, development is taken to comply with a deemed-to-comply provision of the R-Codes if the development complies with — (a) a provision of a local development plan, precinct structure plan or local planning policy if — (i) the provision amends or replaces the deemed-to-comply provision; and (ii) for a provision of a local development plan or local planning policy where the plan or policy is required to be approved by the Commission under the R-Codes — the plan or policy is approved by the Commission; or (b) a provision that — (i) is in a structure plan that was approved before 19 October 2015; and (ii) amends or replaces the deemed-to-comply provision.
Read the source · retrieved 9 September 2026
What changes council by council in Western Australia
The state instruments set the frame. These points are set by each council's own instrument or mapping, so the answer for an address depends on which council it sits in.
- The density code (R-Code) on your lot is set by the local planning scheme map, and it decides whether Part B or Part C of the R-Codes applies to the house and the flat.
- Street setback, lot boundary setback, building height, garage and carport setback, street walls and fences and outbuilding provisions can be modified by a local planning policy or local development plan without WAPC approval, so the numbers your flat must meet may differ from the state defaults.
- Any other deemed-to-comply provision, including the 70m2 floor area cap, can only be modified by a council with WAPC approval, so check whether such an approved policy exists.
- Whether the lot is a heritage-protected place under the scheme decides whether the clause 61 exemption from development approval is available at all.
- A scheme may require development approval for a single house irrespective of the R-Codes, and a scheme can exclude R-Codes provisions outright as the Regulations allow.
For your address
How the $150 report settles this for one site
A Casa preliminary planning report reads the density code and zone from the local planning scheme at your parcel, identifies whether Part B or Part C of the R-Codes applies, and checks the mapped heritage and other overlays that affect the clause 61 exemption. It then sets out the ancillary dwelling pathway for that address, the deemed-to-comply provisions the design must meet, and which of those provisions the local planning framework has modified. It does not replace the building permit process or a council determination.
Common questions
How big can a granny flat be in WA?
The R-Codes deemed-to-comply provision sets a maximum internal floor area of 70m2 for an ancillary dwelling, in both Part B (clause 5.5.1) and Part C (Table 2.8a). A larger unit is not banned, but it loses the deemed-to-comply pathway and must be justified against the design principle that the dwelling stays small scale and incidental to the main house.
Is there a minimum lot size for a granny flat in WA?
The Part D site area rule does not apply to an ancillary dwelling, and the former condition C1(i) of clause 5.5.1 was deleted by the amendment dated 10 April 2024. What limits you on a small lot is the requirement that the flat sits behind the street setback line and does not stop the main house meeting its own open space and outdoor living area.
Do I need council approval for a granny flat in WA?
Not for planning purposes if the flat meets every deemed-to-comply provision of the R-Codes and the lot is not a heritage-protected place, because Schedule 2 clause 61 item 7 of the Local Planning Schemes Regulations exempts it from development approval. You still need a building permit under section 9 of the Building Act 2011, and any departure from deemed-to-comply means a development application.
Can a granny flat be attached to the house?
Yes. The R-Codes definition of an ancillary dwelling says it may be attached to, integrated with or detached from the dwelling.
What happens if my council has its own granny flat policy?
The R-Codes let a local planning policy modify listed deemed-to-comply provisions without WAPC approval and any other provision with WAPC approval. Clause 1B of the deemed provisions then treats compliance with that approved policy as compliance with the R-Codes, so the council policy becomes the standard your design is measured against.
Sources read for this guide
- Residential Design Codes Volume 1 (R-Codes Volume 1), Version 3 published 10 April 2026, Western Australian Planning Commissionread 9 September 2026
- Planning and Development (Local Planning Schemes) Regulations 2015 (WA), official version as at 03 Nov 2024read 9 September 2026
- Building Act 2011 (WA), official version as at 28 May 2026read 9 September 2026
Not covered here
- R-Codes Volume 1 quotes were taken from Casa's cached copy of the wa.gov.au PDF (sha256 18dfd0c7, fetched 2026-09-08 and re-read 2026-09-09). The Regulations, the Planning and Development Act and the Building Act were fetched live from legislation.wa.gov.au on 2026-09-09.
- The R-Codes clause 5.5.1 does not state an occupancy or rental rule for ancillary dwellings, so this guide does not give one. Any such rule would sit in a local planning scheme or policy and was not fetched.
- Part C Table 2.8a limits are presented in prose from the table because the PDF table layout does not extract as a clean sentence. The note below the table is quoted verbatim.
More WA guides
- Dual occupancy rules in WA
- Subdivision rules in WA
- Fast-track approvals in WA
- Height and setback rules in WA
- Do I need a DA in WA?
Granny flat rules in other states
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