(Source: Federal Construction Council: Technical Report No. 50, Publication 1235)
Gross Area | Definition: The sum of all areas on all floors of a building included within the outside faces of its exterior walls, including floor penetration areas, however insignificant, for circulation and shaft areas that connect one floor to another. |
Basis for Measurement: Gross area is computed by physically measuring or scaling measurements from the outside faces of exterior walls, disregarding cornices, pilasters, buttresses, etc., which extend beyond the wall faces. Excluded are areas having less than a six-foot, six-inch clear ceiling height? Measured in terms of gross square feet (GSF): Gross Area = Net Usable Area + Structural Space | |
Description: In addition to all the internal floored spaces covered above, gross area should include the following: excavated basement areas; mezzanines, penthouses, and attics; garages; enclosed porches, inner or outer balconies whether walled or not, if they are utilized for operational functions; and corridors whether walled or not, provided they are within the outside face lines of the building, to the extent of the roof drip line. The footprints of stairways, elevator shafts, and ducts (examples of building infrastructure) are to be counted as gross area on each floor through which they pass. | |
Limitations: Exclude open areas such as parking lots, playing fields, courts, and light wells, or portions of upper floors eliminated by rooms or lobbies that rise above single-floor ceiling height. | |
Exception: Include top, unroofed floor of parking structures where parking is available. | |
Assignable Area (Net Assignable Square Feet – NASF
| Definition: The sum of all areas on all floors of a building assigned to, or available for assignment to, an occupant or specific use. |
Basis for Measurement: Assignable area is computed by physically measuring or scaling measurements from the inside faces of surfaces that form the boundaries of the designated areas. Exclude areas having less than a six-foot, six-inch clear ceiling height unless the criteria of a separate structure are met. Measured in terms of assignable square feet (ASF): Assignable Area = Sum of Area Designated by the Ten Assignable Major Room Use Categories | |
Description: Included should be space subdivisions of the ten major room use categories for assignable space – classrooms, labs, offices, study facilities, special use, general use, support, health care, residential and unclassified – that are used to accomplish the institution’s mission. | |
Limitations: Deductions should not be made for necessary building columns and projections. Areas defined as building service, circulation, mechanical and structural should not be included. | |
Non-assignable Area | Definition: The sum of all areas on all floors of a building not available for assignment to an occupant or for specific use, but necessary for the general operation of a building |
Basis for Measurement: Non-assignable Area is computed by physically measuring or scaling measurements from the inside faces of surfaces that form the boundaries of the designate areas. Exclude areas having less than six-foot, six-inch clear ceiling height unless the criteria of a separate structure are met. Measured in terms of area:
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Description: Included should be space subdivisions of the three non-assignable room use categories – building services, circulation and mechanical – that are used to support the building’s general operation. | |
Limitations: Deductions should not be made for necessary building columns and projections. Areas defined as assignable should not be included. | |
Building Service Area
| Definition: The sum of all areas on all floors of a building used for custodial supplies, sink rooms, janitorial closets, and for public rest rooms. NOTE: Building Service Area does not include assignable areas (e.g., areas classified as 730 – Central Storage and 870 – Central Supplies are not part of Building Service Area). |
Basis for Measurement: Building Service Area is computed by physically measuring or scaling measurements from the inside faces of surfaces that form the boundaries of the designate areas. Exclude areas having less than six-foot, six-inch clear ceiling height unless the criteria of a separate structure are met. | |
Description: Included should be janitor closets or similarly small cleanup spaces, maintenance material storage areas, trash-rooms exclusively devoted to the storage of non-hazardous waste created by the building occupants as a whole and public toilet. | |
Limitations: Deductions should not be made for necessary building columns and projections. Areas central physical plant shop areas, or special purpose rooms, such as linen closets and housekeeping rooms in residence halls, should not be included. Does not include private toilets. | |
Circulation Area | Definition: The sum of all areas on all floors of a building required for physical access to some subdivision of space, whether physically bounded by partitions or not. |
Basis for Measurement: Circulation area is computed by physically measuring or scaling measurements from the inside faces of surfaces that form the boundaries of the designated areas. Exclude areas having less than a six-foot, six-inch clear ceiling height unless the criteria of a separate structure are met. | |
Description: Included should be, but is not limited to, public corridors, fire towers, elevator lobbies, tunnels, bridges, and each floor’s footprint of elevator shafts, escalators and stairways. Receiving areas, such as loading docks, should be treated as circulation space. Any part of a loading dock that is not covered is to be excluded from both circulation area and the gross building area. A loading dock, which is also used for central storage, should be regarded as assignable area and coded as central storage (730). Also included are corridors, whether walled or not, provided they are within the outside facelines of the buildings to the extent of the roof drop line. | |
Limitations: Deductions should not be made for necessary building columns and minor projections. When determining corridor areas, only spaces required for public access should be included. Restricted access private circulation aisles used only for circulation within an organisational unit’s suite of rooms, auditoria, or other working areas should not be included. | |
Definition: The sum of all areas on all floors of a building required for physical access to some subdivision of space, whether physically bounded by partitions or not. | |
Mechanical Area | Definition: The sum of all areas on all floors of a building designed to house mechanical equipment, utility services, and shaft areas. |
Basis for Measurement: Mechanical area is computed by physically measuring or scaling measurements from the inside faces of surfaces that form the boundaries of the designated areas. Exclude areas having less than six-foot, six-inch clear ceiling height unless the criteria of a separate structure are met. | |
Description: Included should be mechanical areas such as central utility plants, boiler rooms, mechanical and electrical equipment rooms, fuel rooms, meter and communications closets, and each floor’s footprint of air ducts, pipe shafts, mechanical service shafts, service chutes, and stacks. | |
Limitations: Deductions should not be made for necessary building columns and projections. Areas designated as private toilets are not included. | |
Net Usable Area | Definition: The sum of all areas on all floors of a building either assigned to, or available for assignment to, an occupant or specific use, or necessary for the general operation of a building. |
Basis for Measurement: Net usable area is computed by summing the assignable area and the non-assignable area. Measured in terms of net usable square feet (NUSF):
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Description: Included should be space subdivisions of the ten assignable major room use categories and the three non-assignable space categories. | |
Limitations: Deductions should not be made for necessary building columns and projections. Areas defined as structural should not be included. | |
Structural Area | Definition: The sum of all areas on all floors of a building that cannot be occupied or put to use because of structural building features. |
Basis for Measurement: Precise computation by direct measurement is not possible under these definitions. It is determined by calculating the difference between the measured gross area and the measured net usable area. Measured in terms of area: Structural Area = Gross Area – Net Usable Area | |
Description: Examples of building features normally classified as structural areas include exterior walls, fire walls, permanent partitions, unusable areas in attics or basements, or comparable portions of a building with ceiling height restrictions, as well as unexcavated basement areas. |
Reference
Federal Construction Council Technical Report No. 50 (Publication 1235), Classification of Building Areas, National Academy of Sciences, Building Research Advisory Board. http://cpdc.uchc.edu/space/definitions.html
