The definitions follow the RICS Code of Measuring Practice (6th Edition).
Gross Floor Area (GFA)
Gross Floor Area (measured in hectares) is the total floor area measured to the external face of the building envelope.
- Includes: All inhabitable space, elevators, hallways, and stairwells on stories containing habitable space. It also includes all structural and technical elements such as columns, internal walls (structural or non-structural), and shafts.
- Excludes: Open spaces such as balconies, fire escapes, open-sided covered ways, and open parking. Any area with a ceiling height lower than 1.5m is also excluded.
- Note: In the United Kingdom, GFA is often referred to as Gross External Area (GEA).
Gross Internal Area (GIA)
Gross Internal Area (measured in hectares) is the total floor area measured to the internal face of the building envelope, excluding the thickness of the external walls.
- Includes: All inhabitable space, elevators, hallways, and stairwells on stories containing habitable space. It also includes all structural and technical elements such as columns, internal walls, and shafts.
- Excludes: Open balconies, fire escapes, open-sided covered ways, and open parking. Any area with a ceiling height lower than 1.5m is also excluded.
- Building Separation: Because GIA excludes external walls but includes internal area, the identification of building separation is critical. Elements not joined by a common form of construction are regarded as separate buildings. If a wall element is part of a larger construction but serves as a building enclosure, 50% of the wall footprint area is included in the calculation.
Net Internal Area (NIA)
Net Internal Area is the total internal floor area of living units and the ground floor, measured to the internal face of the perimeter walls at each floor level.
- Includes: Area occupied by non-structural internal walls, built-in cupboards, and sloping areas or stairs within the habitable area.
- Excludes: Technical shafts, stairwells, elevators, and additional internal walls on the ground floor. All permanent circulation areas—such as landings and corridors—are excluded.
- Note on Double Height: In cases of double-ceiling height, the NIA is counted only once, at the base level.
Site Metrics
Footprint Area
The 2D planar projection of the building's ground-level footprint. This does not include overhangs, balconies, or protruding elements, nor does it account for terrain variations.
Open Parcel Area
The residual area of a parcel not covered by the building footprint. This calculation does not include underground parking or elevated courtyard parking; these areas are treated as open parcel area.
Park Area
The combined area of all manually drawn parks in a scenario. Note that the tool does not auto-generate parks; the total includes any park area that extends beyond the site boundary.
Road Area
The combined area of all roads and paths. If two roads overlap, the overlapping area is counted twice. This total includes roads extending beyond the site boundary.
Restricted Area
The combined area of all restricted zones manually drawn by the user. These areas are not auto-generated.
