If you've looked up a property in Western Australia, you've probably seen a code like R20, R40 or R60 attached to it. These are Residential Design Codes, usually called "R-Codes", and they are one of the biggest factors in what you can build on a block. Get the R-Code wrong and your development plans can fall apart before they start.

This guide explains what the numbers mean, and how the same idea appears under different names in every other Australian state.

What the R-Code Number Represents

The number after the "R" broadly reflects residential density: how many dwellings are expected per hectare of land. A higher number means higher density, smaller minimum lot sizes, and more dwellings permitted on the same block.

As a rough guide under WA's Residential Design Codes:

Key point: The exact minimum and average site areas for each R-Code are set out in the R-Codes tables, and local schemes can vary or override them. Always confirm the figures for your specific lot rather than assuming a standard number.

Why "Minimum" and "Average" Site Area Both Matter

R-Codes usually specify two site-area figures: a minimum and an average. On a multi-dwelling site, each lot must meet the minimum, but the whole development also has to satisfy the average across all lots. This stops developers from cramming the maximum number of tiny lots onto a site.

A simple example: an 800 m² block coded R30, where the average site area is 300 m², has room for two dwellings (800 ÷ 300 = 2.7, rounded down). It is the average, not the minimum, that sets how many dwellings fit. Setbacks, driveway access, open space and parking rules can reduce the number further, because density is the ceiling, not a guarantee.

Dual-Coded Blocks (e.g. R20/R40)

You'll sometimes see a block with two codes, like R20/R40. This means the lower density applies by default, but the higher density can be achieved if you meet extra conditions, often things like connecting to reticulated sewer, meeting design standards, or aged/dependent housing provisions. Dual coding is a common way councils allow gentle density increases without blanket rezoning.

How Other States Control Density

Only WA uses the "R-Code" label, but every state controls residential density, just with different tools:

The vocabulary differs, but the question is always the same: how much land does each dwelling need, and how many will the controls allow?

What Density Controls Don't Tell You

An R-Code (or its interstate equivalent) sets the theoretical dwelling yield, but it never acts alone. Your real capacity also depends on:

How to Check Your Block's Density

Before you buy or plan, you want three numbers: your land size, your density code or minimum lot size, and the resulting maximum dwelling yield. You can look up the zoning and density code for any Australian property using ZoneScout's property search, then confirm the fine detail against your local scheme or with a town planner.

Once you know how many dwellings your land can realistically support, the next step is checking whether the project actually stacks up financially. Our feasibility guide walks through the numbers professional developers use before they commit.

Bottom line: The R-Code (or equivalent) is the starting point for development potential, not the final answer. It tells you the ceiling on density. Setbacks, overlays and design rules decide what you can actually build underneath it.

Not sure what your density code allows?

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