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