The term "floor area" as employed in this chapter means the total interior floor area of a building or structure measured at the inside face of the exterior walls, but excluding stairwells, elevator shafts, lobbies and in multitenant buildings excluding permanent corridors and bathrooms located for common or public usage of the total building rather than for tenant or internal usage, and excluding space occupied by mechanical equipment or space related to the operation and maintenance of the building. (Ord. 1742 § 1 (part), 1999)