“Gross floor area” means the sum of the gross horizontal areas of all floors within the exterior walls of a building, including interior balconies and mezzanines, measured to the interior finished faces of the exterior walls of each such floor, but excluding:

A. Any floor area devoted to mechanical, electrical or communication equipment or uses, as may be required for the operation of the building, including elevators serving the building or devoted to stairwells;

B. Any floor area in a story the ceiling whereof is less than four feet above grade at any point unless the floor area is devoted to office, commercial or service uses;

C. Any floor area used exclusively as parking and/or circulation space for motor vehicles;

D. Any floor area in exterior balconies; and

E. Any floor area that serves as interior common area open space, such as atriums and lobbies (except that the first floor of any atrium or lobby shall constitute gross floor area). (Ord. 1987-1 § 1(D): Ord. 1985-6 § 4 (part); prior code § 5-2-2(BB))