How are site coverage, gross floor area and plot ratio calculated?
Site coverage is measured from the external faces of exterior walls and basement walls. For other structures, such as balconies, terraces and pergolas, the furthest extent of the structure is generally used when calculating site coverage.
Site coverage may include:
- the building footprint at ground level;
- covered structures attached to or forming part of the building; and
- other structures occupying land on the block that contribute to the building footprint.
Formula: Site Coverage (%) = (Area of building footprint and included structures ÷ Total site area) × 100
Gross Floor Area (GFA) is the total area of all floors of a building. It is measured from the external faces of exterior walls, or from the centre lines of walls separating the building from another building.
GFA excludes areas that are reasonably used and necessary solely for:
- fixed mechanical plant;
- bicycle parking and associated end-of-trip facilities; and/or
- basement car parking.
GFA is an important measurement because it is used when calculating plot ratio and may also be used for other planning assessments, such as car parking requirements.
Plot ratio measures the relationship between the total floor area of a building and the size of the site.
It is calculated as:
Plot Ratio = Gross Floor Area ÷ Site Area
For example, a building with a GFA of 500 m² on a block of 1,000 m² would have a plot ratio of 0.5.
Reference: ACT Advisory Note 08 – Working out gross floor area and site coverage
Short Answer
Site coverage, gross floor area (GFA), and plot ratio are measurements used under ACT planning rules to control the scale and intensity of development. Site Coverage measures the proportion of the block occupied by buildings and structures. It includes the building footprint, attached covered structures, and other structures that contribute to the footprint. It is calculated as: Site Coverage (%) = (Area of building footprint and included structures ÷ Total site area) × 100 Gross Floor Area (GFA) is the total area of all floors of a building, measured from the external faces of walls. It excludes areas used solely for fixed mechanical plant, bicycle parking/end-of-trip facilities, and basement car parking. Plot Ratio measures the relationship between the building’s total floor area and the site area: Plot Ratio = Gross Floor Area ÷ Site Area
Detailed Explanation
Under the ACT planning system, site coverage, gross floor area (GFA), and plot ratio are used to measure the size and intensity of a proposed development. These calculations help determine whether a development complies with the relevant planning requirements for the site.
Site coverage measures the area of a block occupied by buildings and structures when viewed from above. It is calculated by comparing the area covered by the development with the total area of the site.
Site coverage is measured from the external faces of exterior walls and basement walls. For structures such as balconies, terraces and pergolas, the furthest extent of the structure is generally used when determining the area counted towards site coverage.
Site coverage may include:
- the building footprint at ground level;
- covered structures attached to or forming part of the building; and
- other structures occupying land on the block that contribute to the building footprint.
Formula:
Site Coverage (%) = (Area of building footprint and included structures ÷ Total site area) × 100
For example, if a building and included structures cover 300 m² of a 600 m² block:
Site Coverage = (300 ÷ 600) × 100 = 50%
This means the development covers 50% of the site area.
Gross Floor Area (GFA) is the total floor area of all levels of a building. It is measured from the external faces of exterior walls, or from the centre lines of walls separating the building from another building.
GFA includes the combined floor areas of the building but excludes areas that are reasonably used and necessary solely for:
- fixed mechanical plant;
- bicycle parking and associated end-of-trip facilities; and/or
- basement car parking.
GFA is an important measurement because it is used to calculate plot ratio and may also be used for other planning assessments, such as determining car parking requirements.
Plot Ratio
Plot ratio measures the relationship between the total floor area of a building and the area of the site. It indicates the intensity of development by comparing how much floor space is provided relative to the size of the block.
Formula:
Plot Ratio = Gross Floor Area ÷ Site Area
For example, if a building has a GFA of 500 m² on a site area of 1,000 m²:
Plot Ratio = 500 ÷ 1,000 = 0.5
This means the total floor area of the building is equal to half of the site area.
No minimum block size does not remove the need for planning assessment.
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