Floor area ratio

In the field of zoning, floor area ratio refers to a limit on how much total space, expressed as a fraction of the total size of the parcel of land involved, may be consumed by the floor or floors of a building or buildings constructed on the parcel. For example, if the relevant zoning ordinance permits construction on a parcel, and construction must adhere to a .1 floor area ratio, then the total area of all floors in all buildings constructed on the parcel must be no more than one-tenth the area of the parcel itself.

Typically, the calculation of area consumed combines the total area of all floors, thus uniting horizontal dimensional limits with vertical dimensional limits into a single parameter. A builder can plan for either a single-story building consuming the entire allowable area in one floor, or a multi-story building that rises higher above the plane of the land, but which must consequently result in a smaller footprint than would a single-story building of the same total floor area. By combining the horizontal and vertical limits into a single figure, some flexibility is permitted in building design, while achieving a hard limit on at least one measure of overall size. One advantage to fixing this parameter, as opposed to others such as height, width, or length, is that floor area correlates well with other considerations relevant to zoning regulation, such as total parking that would be required for an office building, total number of units that might be available for residential use, total load on municipal services, etc. The amounts of these things tend to be constant for a given total floor area, regardess of how that area is distributed horizontally and vertically.

References

• Meriam, Dwight (2004). The Complete Guide to Zoning. McGraw-Hill. ISBN 0071443797.