“Floor space ratio” (FSR), an alternative term for FAR, is used in the United States and Canada. In the United Kingdom and Singapore, the term “plot ratio” is used as an alternative.
FAR is the abbreviation for Floor Area Ratio. FAR is defined as ‘the ratio of a building’s total floor area (Gross Floor Area) to the area of land upon which it is built’. The constructed area would include the basic structure, exterior walls, staircases or lobby space, if any. The ratio is obtained by dividing the total area built by the area of parcel of land upon which it is built.
The Gross Floor Area includes all the space within the exterior walls of the construction under study, including all habitable and inhabitable spaces in it.
FARs include all the habitable area in the building, and excludes areas such as parking lots. The habitable areas, according to the specified building codes, are the spaces used for living, cooking, eating, and sleeping. Toilets, closets, corridors, halls, utility and storage areas are not considered as habitable spaces.
FAR = (Gross Floor Area) / (Area of the plot)
FAR is used for developing the zoning codes by the government’s planning department. The zoning code for a parcel of land mentions the permissible floor space that may be constructed on it. The architect may take up the entire floor space in a single story or may go for multiple floors or stories, having a comparatively smaller footprint. The vertical and horizontal limits have to be adjusted, so as to abide by the permissible height and FAR for that parcel.
A higher FAR for an area is indicative of more floor space availability in that area. Also, it has been observed that zones within higher FARs are known to have a higher land price.
Different cities have different laws regarding the maximum Floor Area Ratio that a building can occupy. An FSR map, charts the maximum property that can be constructed for commercial and non-commercial purposes in a particular region. That is, it limits the total area that can be constructed upon a parcel of land available.
Calculation of FAR
Step 1: Calculate the area of the parcel by multiplying the length and width of the construction site available.
Step 2: Calculate the area of each of the stories in the planned building.
Step 3: Add up the individual footprint of each story to obtain the total square footage.
Step 4: Divide the total square footage of the building’s stories with the area of the parcel or the footage of the building.
Area of parcel or plot = 38,000 sq. ft
The gross floor area = 5,000 sq. ft + 3,000 sq. ft + 4,000 sq. ft + 3,000 sq. ft = 15,000 sq. ft
Floor area ratio (FAR) = 15,000/38,000 = 0.3947 FAR