GSF = Gross Square Feet: The sum of all areas on all floors of a building included within the outside faces of its exterior walls, including all vertical penetration areas, for circulation and shaft areas that connect one floor to another.

ASF = Assignable Square Feet: The sum of all areas on all floors of a building assigned to, or available for assignment to, an occupant or specific use. (Classrooms, labs, offices, study facilities, special use, general use, support, health care, residential, and unclassified – that are used to accomplish the institution’s mission).

Non ASF = Non Assignable Square Feet: The sum of all areas on all floors of a building not available for assignment to an occupant or for a specific use, but necessary for the general operation of a building. (Building services, circulation, and mechanical that are used to support the building’s general operation).

SSF = Structural Square Feet: The sum of all areas on all floors of a building that cannot be occupied or put to use because of structural building features.  (Exterior walls, fire walls, permanent partitions, unusable areas in attics or basements, or comparable portions of a building with ceiling height restrictions).

Structural Area = Gross Area minus Assignable and Non Assignable Area.

Source of Information: National Center for Education Statistics, Institute of Education Sciences “Post-Secondary Education Facilities Inventory and Classification Manual (FICM) 2006 Edition”.