Floor Area Ratio (Zoning)
The zoning intensity number a site's buildable size turns on: FAR = gross building floor area / lot area, and where a limit is set the maximum buildable floor area = FAR_limit x lot area. A 30,000 SF building on a 20,000 SF lot is FAR 1.5; a 2.0 cap allows 40,000 SF, so 10,000 SF of capacity remains. FAR caps bulk without dictating footprint or height -- a FAR of 1.0 is one story over the whole lot or two over half. The catch is the definition of floor area (whether parking, basements, and mechanical count), which varies by municipality; enter the gross figure the local code defines. A screening aid; the zoning ordinance and planning authority govern.
Formula and source
FAR = building_floor_area / lot_area; max_buildable = FAR_limit x lot_area; remaining = max_buildable - existing_floor_area.
Floor area ratio, the municipal zoning intensity measure, by name; the zoning ordinance and planning authority govern.
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