1. Gross Square Feet (GSF) = Net Usable Square Feet + Structural Square Feet
    1. Definition:  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.
    2. Basis for Measurement: Gross Square Feet is computed by physically measuring or scaling measurements from the outside faces of exterior walls, disregarding architectural and structural projections such as cornices, pilasters, buttresses, etc., that extend beyond the exterior building wall faces. Exclude areas having less than a 3-foot clear ceiling height unless the criteria of a separate structure are met. Round up GSF to the nearest whole number. Within the building, count vertical circulation space-whether floored or not, such as vertical mechanical, electrical & elevator shafts at each floor.
    3. Examples of Included Spaces:
      1. All interior assignable spaces  Inside balconies utilized for operational functions
      2. Basements and attics  Enclosed unfinished areas, if >= 3’0” in height
      3. Garages  Vertical circulation w/wo floors (count at each floor)
      4. Enclosed porches or portion of porch covered  Mechanical and electrical shafts (count at each floor)
      5. Penthouses  Elevators and elevator shafts (count at each floor)
      6. Mechanical equipment floors (interstitial)  Piers (structural only-count surface area of decking)
      7. Public areaways, lobbies, and mezzanines
    4. Examples of Excluded Spaces:
      1. Attics without flooring
      2. Parking lots (uncovered)
      3. Light wells
      4. Playing fields
      5. Portions of upper floors eliminated by rooms or lobbies which rise above single floor height
      6. Floored areas with less than 3.0” clear headroom (unless they can be properly designated and used as mechanical or custodial areas
      7. All open to the weather spaces with no overhead covering (e.g. exterior corridors, porches, balconies, courts, etc.)
         
  2. Net Usable Square Feet (NUSF) = Assignable Square Feet + Nonassignable Square Feet
    1. 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.
    2. Basis for Measurement. Net Usable Square Feet is computed by summing the Net Assignable Square Feet and the Nonassignable Square Feet. 
       
  3. Net Assignable Square Feet (NASF) = Sum of the 10 Major Space Use Categories of Assignable Space
    1. Definition. The sum of all areas on all floors of a building assigned to, or available for assignment to, an occupant or specific use.
    2. Basis for Measurement. Net Assignable Square Feet is computed by physically measuring or scaling measurements from the inside faces of surfaces such as walls, partitions or doors, etc., that form the boundaries of the designated areas. Space is to be covered by a ceiling 3'-0" or higher, and preferably but not required in special circumstances, enclosed on all sides by walls, partitions, doors, or functionally equivalent. Round up ASF to the nearest whole number. Include columns or similar structural elements, built-in or freestanding furniture and equipment, and alcoves and other similarly recessed areas. Exclude areas having less than a 3-foot clear ceiling height unless the criteria of a separate structure are met.
       
  4. Nonassignable Square Feet = Sum of the Three Major Space Use Categories of Nonassignable Space
    1. 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 (Building Service, Circulation, Mechanical).
    2. Basis for Measurement. Nonassignable 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 3-foot clear ceiling height unless the criteria of a separate structure are met.
       
  5. Structural Square Feet = Gross Square Feet – Net Usable Square Feet
    1. Definition. The remaining area within the gross square footage of a building is structural or “construction” square feet, which cannot be occupied or put to use. This is defined as the sum of all areas on all floors that cannot be occupied or put to use because of structural building features. This is the mathematical difference between Gross Square Feet and Net Usable Square Feet. Examples of building features normally classified as structural areas include exterior walls, fire walls, permanent partitions, unusable area in attics or basements, or comparable portions of a building with ceiling height restrictions, as well as unexcavated basement areas.
    2. Basis for Measurement. Precise computation by direct measurement is not possible under this definition. Structural Square Feet is determined by calculating the difference between the measured gross square feet and the measured net usable square feet