Plot ratio (WA R-Codes)
Plot ratio is the WA equivalent of FSR, defined in R-Codes Volume 1 Part C. Applies to grouped + multiple dwellings R30+. Single houses controlled by site coverage.
Ask Chalkline about this →Plot ratio is the Western Australian equivalent of FSR (Floor Space Ratio), defined in R-Codes Volume 1 Part C. It is the maximum gross floor area (GFA) as a ratio of site area, applied to grouped and multiple dwellings at R30 density and above. Single houses are controlled by site coverage and setbacks, not plot ratio. The control limits how much enclosed floor area can be built on a lot of given size, preventing over-development of suburban blocks. Verified per R-Codes Volume 1 Part C (2026-05-23).
Plot ratio calculation:
Plot ratio = Gross floor area (GFA) / Site areaExample: a 600 m² lot with a plot ratio control of 0.5:
- Maximum GFA = 0.5 × 600 = 300 m².
Plot ratio by R-Code (indicative):
| R-Code | Plot ratio | Notes |
|---|---|---|
| R10-R25 | N/A (single houses; site coverage instead) | Site coverage typically 50% |
| R30 | ~0.5 | Grouped dwelling permitted |
| R40 | ~0.6 | Higher-density grouped |
| R60 | ~0.75 | Multiple dwellings |
| R80 | ~1.0 | Volume 2 territory |
| R100 | ~1.0-1.5 | Volume 2 apartments |
| R160+ | ~1.5-2.0+ | High-density apartments |
(Exact ratios are set in the council’s Local Planning Scheme calling up the R-Codes. Check the LPS.)
What counts as Gross Floor Area:
| Included | Excluded |
|---|---|
| All enclosed floor area at all levels | Open verandahs and balconies (typically) |
| Garage internal floor area | Open carports |
| Habitable rooms (bedrooms, living, kitchen, bath) | Outdoor terraces |
| Internal corridors and stairs | External walls measured as part of the structure |
| Loft spaces with 2.1 m+ ceiling | Sub-floor (under floor; not habitable) |
| Habitable basements | Storage spaces (under specific dimensions) |
R-Codes Volume 1 Part C has a precise definition of GFA. Always cross-check the council’s LPS: some councils have minor variations.
Why plot ratio doesn’t apply to single houses:
Single houses on standard suburban lots (R10-R25) are controlled by:
- Site coverage: maximum % of site area covered by buildings.
- Setbacks: distance from each boundary.
- Open space: minimum non-built area.
- Height: maximum eave or ridge height.
These controls together effectively cap the floor area without needing a separate plot ratio. Plot ratio kicks in at R30+ where grouped or multiple dwellings introduce more density.
Worked example: dual occupancy on R30:
A 800 m² lot at R30 density (plot ratio 0.5):
- Maximum GFA = 0.5 × 800 = 400 m² total across both dwellings.
- Two dwellings averaging 200 m² each, or one larger + one smaller.
- Plus garages internal floor (each 25-40 m²) brings total internal area to ~250 m² per dwelling.
If the design exceeds 400 m² total GFA, the proposal needs to argue under the Design Principle pathway against the R-Codes’ plot ratio principle.
Worked example: apartments on R80:
A 1,000 m² lot at R80 density (plot ratio 1.0):
- Maximum GFA = 1.0 × 1,000 = 1,000 m².
- Could support ~10 apartments of 100 m² each, or 12-15 smaller apartments.
- Triggers Volume 2 design requirements (apartment design guidelines, communal open space, etc.).
Common defects:
- GFA calculation includes balcony or carport: incorrect; reduces apparent GFA limit.
- Plot ratio applied to single house at R20: confusion with multi-dwelling; not applicable.
- Site area used for plot ratio includes an excluded zone (e.g. road reserve, easement): inflates the apparent capacity.
- Ground-floor basement counted toward GFA when it’s truly sub-floor: definition issue; check Volume 1 Part C.
- Garage assumed open carport: garage internal floor is GFA; open carport is not.
Comparison to other state FSR/density controls:
| State | Equivalent | Application |
|---|---|---|
| WA | Plot ratio (this), R-Codes Volume 1 Part C | R30+ grouped/multiple |
| NSW | Floor Space Ratio (FSR), LEP cl 6.5 typically | Most non-single residential |
| VIC | Plot ratio (in some schemes) | Limited; mostly setbacks/site coverage |
| QLD | Site cover + height + setbacks | Plot-ratio-like controls vary |
| SA | Site density (PDI Code) | Per zone |
| TAS | Site coverage (TPS) | Per zone |
| NT | Plot ratio in some zones | Per zone |
Builder takeaway:
- For WA residential at R30+, check the plot ratio for the zone before sizing the design.
- Confirm what’s included/excluded in GFA per Volume 1 Part C and any LPS variations.
- For single houses at R10-R25, plot ratio doesn’t apply: use site coverage and setbacks.
- The 2025 R-Codes amendments tightened plot ratio in some zones; if working off pre-2025 design templates, recheck.
Also known as: PR; gross floor area ratio; WA FSR; floor area ratio (WA).
Category: Approvals & DA.
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Last updated: 2026-05-23. Verified: 2026-05-23. Quarterly review for currency.