Western Australia · Planning guide
Dual occupancy rules in WA
In WA a dual occupancy is two grouped dwellings on one lot, and whether you can build one depends on the density code (R-Code) that your local planning scheme applies to the lot. Part D of the Residential Design Codes Volume 1 sets a minimum and an average site area per dwelling for each R-Code in Table D, and the decision-maker cannot vary those figures except as the R-Codes or the scheme allow. Erecting a grouped dwelling is not on the list of works exempt from development approval, so a development application is needed. The R-Codes then give a deemed-to-comply pathway for setbacks, open space, height and parking, with a design principle pathway for anything that departs from it.
Sources read on 9 September 2026. Provisions are quoted word for word from the instrument.
What a dual occupancy is in WA terms
The R-Codes do not use the phrase dual occupancy. They distinguish a single house, which stands on its own green title or survey-strata lot, from a grouped dwelling, which is one of a group of two or more dwellings on the same lot where no dwelling sits vertically above another. Two villas or two townhouses side by side on one parent lot are grouped dwellings. Units stacked on top of each other are multiple dwellings.
This matters because the site area rules, and the choice between Part B and Part C of the R-Codes, both depend on the dwelling type. Part B covers grouped dwellings in areas coded R25 and below, Part C covers grouped dwellings coded R30 and above.
GROUPED DWELLING - a dwelling that is one of a group of two or more dwellings on the same lot such that no dwelling is placed wholly or partly vertically above or below another, except where special conditions of landscape or topography dictate otherwise, and includes a dwelling in a strata titles scheme with common property.
Read the source · retrieved 9 September 2026
SINGLE HOUSE - a dwelling standing wholly on its own green title or survey-strata lot, together with any easement over adjoining land for support of a wall or for access or services and excludes dwellings on titles with areas held in common property.
Read the source · retrieved 9 September 2026
The density code decides how many dwellings fit
Every residential lot in WA carries a density code such as R20, R30 or R40, shown on the local planning scheme map. The R-Codes design principle for site area is simply development of the type and density indicated by the density code designated in the scheme. Part D clause 1.1 then turns that code into numbers through Table D, which lists a minimum site area and an average site area per dwelling for each code and dwelling type.
For a grouped dwelling the minimum site area is measured as the land occupied by the dwelling itself plus all other areas set aside for the exclusive use of its occupants, whether or not they are contiguous.
The R-Codes illustrate the two-number test with worked figures. Figure 1.1b shows the R25 requirements as a minimum of 300m2, an average of 350m2 and a battleaxe site of 425m2. Figure 1.1c shows R50 as a minimum of 160m2 and an average of 180m2. Other codes have their own figures in Table D, and you must read the row for your code rather than assume a general number.
Part A is explicit that the decision-maker cannot vary the minimum or average site area in Table D except where the R-Codes or the scheme allow it. The allowed variations include a WAPC-approved lot, an existing lot with permanent legal access to a public road, and reductions of up to one third for aged or dependent persons' dwellings and single bedroom dwellings in areas coded R25 and below.
Development of the type and density indicated by the density code designated in the scheme. Development which complies with the dwelling type and site area requirements set out in Table D and the following provisions. The minimum site area set out in Table D is calculated as follows: i. in the case of a single house, the area of a green title lot or survey-strata lot; or ii. in the case of a grouped dwelling, the area of land occupied by the dwelling itself, together with all other areas whether contiguous or not, designated for the exclusive use of the occupants of that dwelling.
Read the source · retrieved 9 September 2026
R25 site area requirements (min 300m2 avg 350m2, battleaxe 425m2). R50 site area requirements (min 160m2 avg 180m2, battleaxe 160m2).
Read the source · retrieved 9 September 2026
The decision-maker shall not vary the minimum or average site area per dwelling requirements set out in Table D except as provided for in the R-Codes Volume 1 or the scheme.
Read the source · retrieved 9 September 2026
The following variations to the minimum and average site area set out in Table D may be made: i. in the case of a single house, grouped dwelling or multiple dwelling; the area of a lot, survey-strata lot or strata lot approved by the WAPC; or ii. the area of any existing lot, survey-strata lot or strata lot with permanent legal access to a public road, notwithstanding that it is less than that required in Table D.
Read the source · retrieved 9 September 2026
In areas coded R25 and below; for an aged or dependent persons’ dwelling (in accordance with Part B, 5.5.2 C2.1-C2.4) or a single bedroom dwelling (in accordance with Part B, 5.5.3 C3) that is the subject of a proposed development, the minimum and average site area of Table D may be reduced by up to one third.
Read the source · retrieved 9 September 2026
Battleaxe and corner lots
Rear battleaxe sites are common for a second dwelling behind an existing house. In areas coded R40 and below the access leg counts toward the site area, but only up to 20 per cent of the site area required by Table D. In areas coded R50 and above the access leg is excluded and the effective lot area must meet the minimum on its own.
A corner truncation to a public street can add up to 20m2 to the adjoining lot for site area purposes. If the battleaxe site abuts a right-of-way or a reserve, half the width of that reserve up to a depth of 2m can also be added.
in the case of a lot with a corner truncation to a public street, up to a maximum of 20m2 of that truncation shall be added to the area of the adjoining lot, survey-strata lot or strata lot as the case may be (refer Figure 1.1a); ii. in areas coded R40 and below; in the case of a rear battleaxe site, the site area is inclusive of the access leg provided that the area of the access leg contributes no more than 20 per cent of the site area as required by Table D (refer Figure 1.1b);
Read the source · retrieved 9 September 2026
iii. where the battleaxe lot (excluding the access leg) adjoins or abuts a right-of-way or reserve for open space, pedestrian access, school site or equivalent, half the width of the right-of-way or reserve (up to a maximum depth of 2m) may be added to the site area (refer Figure 1.1b and 1.1c); or iv. in areas coded R50 and above; in the case of a battleaxe lot, the vehicle and/or pedestrian access leg and associated truncations shall be excluded from the calculation of minimum site area to achieve an effective lot area consistent with the minimum site area required in Table D (refer Figure 1.1c).
Read the source · retrieved 9 September 2026
Approval pathway for grouped dwellings
Clause 61 of the deemed provisions in the Local Planning Schemes Regulations exempts a single house that meets deemed-to-comply from development approval. It does not exempt the erection of a grouped dwelling. Two dwellings on one lot therefore need development approval from the local government under clause 60, and the R-Codes flowchart routes all other residential development to a development application.
Once an application is lodged the R-Codes work in two layers. A proposal that meets every deemed-to-comply provision must not be refused. A proposal that departs from one provision is judged on merit against the corresponding design principle, and only for that element. Deemed-to-comply proposals also avoid advertising to neighbours.
Open space for a grouped dwelling is measured on the area allocated for that dwelling's exclusive use plus its proportionate share of common property. Part B Table B lists the minimum open space and outdoor living area for each code, and where common open space is provided the requirement for a dwelling with direct access to it can be reduced by up to 20 per cent.
The erection of, or alterations or additions to, a single house on a lot. (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
Where an application does not meet a deemed-to-comply provision(s) of the R-Codes Volume 1 and addresses a design principle(s), the decision-maker is required to exercise judgement and undertake a merit-based assessment to determine the proposal. The decision-maker shall not refuse to grant approval to an application where the application satisfies the deemed-to-comply provisions of the R-Codes Volume 1 and any relevant provision of the scheme and local planning framework.
Read the source · retrieved 9 September 2026
Open space provided in accordance with Table B (refer Figure Series 6). The site of the grouped dwelling, for the purpose of calculating the open space requirement, shall include the area allocated for the exclusive use of that dwelling and the proportionate share of any associated common property. Where communal open space is provided as common property in a grouped dwelling development, the open space required for any grouped dwelling having legal and direct physical access to that open space may be reduced by up to 20 per cent of the required open space area
Read the source · retrieved 9 September 2026
Higher codes and the medium density provisions
Grouped dwellings in areas coded R30 and above are assessed under Part C of the R-Codes, which has its own primary controls in Table C for site cover, building height, street setbacks and lot boundary setbacks, along with garden, tree canopy and dwelling size elements. Table C applies except where the local planning framework modifies it.
Part D also allows the average site area to be reduced by up to 35 per cent in areas coded R30 to R40 for an accessible dwelling built to gold level universal design or a small dwelling, provided no site is under 100m2 and, for four or more dwellings, no more than half of them use the reduction.
Primary controls of Table C apply, except where modified by the local planning framework, in which case development complies with the controls set out in the applicable local planning instrument.
Read the source · retrieved 9 September 2026
In areas coded R30 to R40; for an accessible dwelling designed to gold level universal design (in accordance with Part B, 5.5.4 C4 or Part C, C2.7.2), or a small dwelling (in accordance with Part B, 5.5.5 C5 or Part C, C2.9.1) that is the subject of a development proposal, the minimum and average site area of Table D may be reduced by up to 35 per cent, provided that: i. for single houses and grouped dwellings, no site is less than 100m2; and ii. for development or subdivision of 4 or more dwellings or sites, the site area reduction is limited to a maximum 50 per cent of the total number of dwellings or sites.
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 R-Code density on each lot is set by the local planning scheme map, and it is the single biggest variable for a dual occupancy.
- A scheme can include split codes, dual codes or clauses that amend, replace, augment or exclude R-Codes provisions, so the Table D figure may be conditional on criteria in the scheme.
- Local planning policies and local development plans can modify street setbacks, lot boundary setbacks, building height, garage setbacks, fencing and other listed provisions without WAPC approval, which changes the deemed-to-comply envelope for the second dwelling.
- Older structure plans can still amend or replace deemed-to-comply provisions under clause 1B of the deemed provisions.
- Heritage-protected status under the scheme changes the exemption position and the assessment matters the council must consider.
For your address
How the $150 report settles this for one site
A Casa preliminary planning report reads the density code from the local planning scheme at your parcel, applies the Table D minimum and average site areas for that code and dwelling type, and accounts for the battleaxe and truncation adjustments in Part D. It identifies whether Part B or Part C governs the design and lists the mapped overlays and local policies that modify the deemed-to-comply provisions. It gives you the pathway and the site area arithmetic for that address, not a council approval.
Common questions
What R-Code do I need for a dual occupancy in WA?
There is no single answer, because Table D of the R-Codes gives a different minimum and average site area for every code. The test is whether your lot area, adjusted under clause C1.1.3, delivers the Table D minimum for each dwelling and the average across both. The R-Codes' own worked example for R25 is a minimum of 300m2 and an average of 350m2 per dwelling.
Can council approve a dual occupancy if my lot is slightly under the Table D size?
Not on its own. The R-Codes say the decision-maker shall not vary the Table D minimum or average site area except as the R-Codes or the scheme provide. The WAPC, in consultation with the council, can approve lots up to five per cent smaller under design principle P1.1.2 where specific criteria are met, and Part D lists other allowed reductions.
Do I need development approval for two grouped dwellings?
Yes. The clause 61 exemption in the deemed provisions covers a single house that meets deemed-to-comply, not the erection of a grouped dwelling, so clause 60 requires development approval from the local government.
Does a battleaxe access leg count as site area?
In areas coded R40 and below it counts, but only up to 20 per cent of the Table D site area. In areas coded R50 and above the access leg is excluded and the effective lot area must meet the minimum by itself.
What is the difference between a grouped dwelling and a multiple dwelling?
A grouped dwelling is one of two or more dwellings on the same lot with none placed vertically above another. A multiple dwelling has part of one dwelling's plot ratio area above another. The distinction changes the Table D figures and which part of the R-Codes applies.
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
Not covered here
- Table D itself is a multi-column table and its rows do not extract as verbatim sentences, so this guide quotes the R-Codes' own figure captions for R25 and R50 rather than reproducing every row. The full schedule for R2 to R100-SL is in Table D of the cached PDF.
- 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 were fetched live from legislation.wa.gov.au on 2026-09-09.
- Design principle P1.1.2 (WAPC approval of lots up to five per cent smaller) is summarised from the cached text and its full criteria list is not reproduced here.
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