“Story” means that portion of a building, included between the surface of any floor and the surface of the floor next above it, or if there is no floor above it, then the space between the floor and the ceiling next above it. If the finished floor level directly above a usable or unused under-floor space is more than six feet above grade as defined in this chapter for more than 50 percent of the total perimeter or is more than 12 feet above grade as defined in this chapter at any point, such usable or unused underfloor space shall be considered as a story. (Ord. 6245 § 3, 2009; Ord. 4229 § 2, 1987.)