What is The Minimum Lot Size for R20 Zoning? R-Codes Decoded

R-Codes Decoded: What is the minimum lot size for R20 Zoning?

When subdividing or developing property in Perth, it’s essential to know the minimum lot sizes for different density zones. R20 is the most common zoning code in Perth, so if you’re planning to develop in the suburbs, it’s likely you’ll be working with an R20 zoned block. 

If your property is zoned as R20, you should be aware of how its minimum and average lot sizes differ from other higher-density zones, such as R30 and R40. 

The minimum lot size based on the new R20 zoning is 350m2. However, not all lots in a subdivision project can be at this minimum size – an average of 450m2 is also required per lot for an R20 zoned property. If you’re looking to subdivide a rear lot or battleaxe, each resulting lot will generally need a minimum of 450m2.  

Many R-codes codes now have smaller lot sizes, adding flexibility and helping provide enough housing as Perth’s population grows. The R-codes also specify guidelines on property setbacks, minimum frontage, outdoor living space and other guidelines to ensure a great quality of life for residents. 

Read on to learn more about the minimum lot size for R20 zoning in Perth.

What Is Zone R20 When It Comes To Perth Property?

It’s common for new and even experienced developers to have questions about Western Australia’s density coding. Whether you’re buying a site or planning to develop a property you already own, the R-code of your block will determine what you can do with the land. 

When subdividing your Perth property, the main factors that guide your project include the lot’s size and zoning. The residential design code is specified in Perth’s state planning policy, so there’s a corresponding number for every residential area. The code consists of the letter “R” and is followed by a number value, such as R20, R40 or R60.

What do these R-codes mean? Put simply, the number shows the maximum number of residences that are allowed per hectare. For example, the density code R20 shows 20 dwellings could be constructed per hectare on R20 coded land. 

Thus, a 1000m2 block theoretically contains this subdivision potential: 

1000 x (20 /10000) = 2 dwellings per 1000m2

If you do the math manually, you may notice that the number you get is slightly different to the official guidelines on lot areas. 

The property areas and other building guidelines have evolved over time to accommodate the need for higher-density housing in Perth. 

Every density code includes published minimum and average lot area requirements, meaning that the average lot size needs to meet a certain threshold across an entire subdivision project. This allows developers to divide their property into lots of varying sizes while ensuring each residence has enough space. 

When it comes to building on an R20 lot, there are additional requirements that must also be met, including:

  • Minimum frontage of 10m
  • 50% of the lot should be open space
  • 30m2 outdoor living space per dwelling

What Is The Minimum Lot Size For Zone R20?

An R-Code of R20 means that an average of 450m² is required per dwelling. The table below is a guide as to how many dwellings could potentially be developed on a lot coded R20:

Lot Size450-899m² 900-1,349m²1,350-1,799m²1,800-2,249m²2,250m² and over
Potential Dwellings12345 or more

Detailed information on minimum and average lot sizes can be found in WA’s official Residential Design Codes
These guidelines were most recently adjusted in 2019, when the average lot size required for R20 zoned areas was dropped from 500m² to 450m² , and the minimum lot size was reduced to 350m². Other significant changes to WA’s town planning rules include allowing non-family members to occupy “granny flats” (ancillary dwellings).

Can You Subdivide A Zone R20 Lot?

Yes, an R20 zoned lot of at least 900m² can potentially be subdivided. You’ll need to meet some minimum requirements, including:

  • A minimum of 350m2 per lot
  • An average area of 450m2 across all new lots 
  • A minimum area of 450m2 for rear strata or battleaxe block subdivisions 

Wise investors have many opportunities due to R-Code changes in Perth, and you may find yourself able to subdivide an R20 lot that previously was not permitted. 

If you’re currently searching for an investment property, understanding the codes allows you to locate a property with a large enough land area to be subdivided. Because of this, the price isn’t always the biggest factor in the real development potential of the property. 

Before purchasing land in Perth, you should always thoroughly understand what the property’s R-code means for its future development, and any limitations you need to follow. Subdivision is also a lengthy process, so ensure you allow enough time for each stage of the applications to be approved. 

Battleaxe Subdivisions on R20 Lots 

A popular way of subdividing land is by creating one lot that fronts a street and one lot located at the site’s rear. The rear block (or rear strata) is linked to the street through a driveway situated along the side of the lot. 

This kind of subdivision is often known as a “battleaxe” subdivision. The accessway to the lot’s rear can either be the rear lot’s exclusive property or common property. This is an important issue since it affects the requirements for minimum lot size. 

If the driveway is defined as common property, the two new lots must comply with requirements for minimum lot size. For R20 lots, this would be 350m2. However, the common property means the battleaxe block can meet the minimum lot size rather than the average. 
If the accessway leading to the rear lot is the exclusive property of that lot, the rear lot must comply with minimum lot requirements for “battleaxe” lots as defined by the property’s R-code. For R20 zoning, this would be 450m2.

What Size Building Can I Build On Zone R20?

Type Of Dwellings 

On an R20 zoned lot, the existing R-code guidelines allow for a single house or separate dwellings as well as grouped dwellings, such as townhouses. Multiple dwellings like apartment buildings are also allowed, subject to development approval. 

Building Size And Height 

Building size and height in Perth may be specified by local planning policies and development plans, under the jurisdiction of a local council. These local codes will designate one of three categories, ranging from single-level development to three-level development. 


‘Frontage’ refers to the width of the lot at the point where it meets the street. R20 zoning requires a minimum frontage of 10m², meaning many R20 lots are classified as small or narrow blocks

Open Space

R20 zoning requires a minimum open space of 50% of the site. Meanwhile, the minimum open space for outdoor living is 30m². 

An important factor when meeting open space requirements is the accessway to rear lots. You can use a simple yet effective solution of allowing a 70m² common driveway along the side of your property. This becomes the development’s common property and adds 70m² of open space to the affected lots.

What Is Dual Density Coding?

Some areas of Perth contain lots with dual residential density coding – also known as “split residential density” or “bonus zoning”. This measure is designed to offer greater flexibility to developers, helping provide housing for Perth’s growing population. 

For instance, dual density code R20/25 shows that either development or subdivision applications can be assessed using either code. By default, dual-density codes are evaluated at the ‘lower’ R-code (which is lower-density). 

To have the application assessed at the ‘higher’ R-code – under higher-density zoning rules – you’re required to submit an application to the West Australian Planning CommissionCity Council for a case-by-case review. 

This means a dual density R20/25 property will have development applications assessed at R20 by default, but applications at R25 may be accepted if a case is made to the council. 

Generally, these developments are approved where the provision of higher-density housing would be beneficial to the community. 

Benefits of Dual Coding 

Dual zoning gives property owners more flexibility about how to subdivide Perth land. 

Dual-density coding also offers opportunities for infill development so councils can meet subdivision targets contained in state planning policies.

Another significant benefit is that it provides local councils with a way to significantly influence the development type and quality within their boundaries. 

They trade higher densities to land developers in return for more influence on the type, size, and quality of development.

What If I Don’t Have Enough Land For Subdivision?

R-Codes are applied to all Perth properties. Besides determining lot sizes they also regulate various design elements, including the type, height and size of any proposed developments. 

If you don’t have enough land to subdivide your block, there are some alternative options:

Appeal To The Planning Commission 

It’s possible to secure special approval for 5% variation in the lot’s average size. It’s worth noting this process takes some time; there is no guaranteed approval.

Purchasing Neighbouring Properties

 If you’re able to purchase adjacent land, the extra area can be incorporated into the existing lot. You cannot use this option to split a lot into single green titled lots. Instead, it’s for building or survey strata developments. 

Granny Flats

Adjustments to the rules related to granny flats in WA now allow homeowners to rent them out to non-family member tenants. This move was implemented to reduce the pressure on rental housing in Western Australia. It also creates more opportunities for homeowners to earn rental income. 

Based on the new regulations, you can construct granny flats in all residential zones. The minimum lot area to build a granny flat in Perth is 450m². A maximum of one main home and one granny flat is permitted per block.  

The granny flat’s size must be a maximum of 70m², and you’ll need to meet other requirements, like building setback. The exception is when the council allows a different maximum under application. 

Regardless, building a granny flat on your Perth property is a viable option if you don’t have enough land to subdivide. Be aware that once you’ve built a granny flat, you’ll no longer be able to subdivide in future, so always consider your long-term plans before construction.

Related Questions:

What Is R20/40 Zoning?

R20/40 is a dual density code under WA local government regulations. The first – or lower – density is applied by default and serves as the benchmark. Therefore, applications would be processed at R20 unless special permission is obtained to be assessed under R40 zoning. 

What Is The Plot Ratio In R Codes?

The plot ratio in Perth R-codes is the percentage of living area as a proportion of the land area. The lot size is multiplied by the maximum plot ratio to determine the maximum floor space that can be built on the block. 

When it comes to multi-storey developments, the floor space of all levels must meet plot ratio requirements, not just the ground level (or building footprint). 


This article is published in good faith and for general informational purposes only. It does not take into consideration your individual circumstances and does not constitute an estimate for any specific project. Central Avenue Homes does not make any warranties about the ongoing completeness, reliability and accuracy of this information. Construction costs and other financial details vary and you should always seek a specific quote.

Greg Grainger

Greg has over 40 years of experience in the WA building industry starting as a carpenter joiner.

He is entrenched in the local industry and has served on the board for MBAWA (Master Builders Australia WA) for over 10 years and was a founding director of Wesbuilders Cooperative for over 11 years.

With this experience he is able to quote accurately on new projects without the huge increase to provisional sum allowances.

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