In 1996, the American National Standards Institute (ANSI) adopted a standard for measuring single family residential buildings. This standard was last revised in 2003, and is called the American National Standard Z765-2003. The ANSI standard bases floor area calculations on the exterior dimensions of the building at each floor level, including all interior walls and deducting voids.
Finished area, sometimes referred to as “Gross Living Area” (GLA), is space that is intended for human occupancy and is:
- Heated by a conventional heating system or systems (forced air, radiant, solar, etc.) that are permanently installed in the dwelling – not a portable heater – which generates heat sufficient to make the space suitable for year-round occupancy.
- Finished, with walls, floors and ceilings of materials generally accepted for interior construction and with a ceiling height of at least seven feet, except under beams, ducts, etc. where the height must be at least six feet four inches.
- Directly accessible from other living area (through a door or by a heated hallway or stairway).
More information on Z765-1996, Z765-2003, and other ANSI standards can be found at American National Standards Institute Website.