"Accessory building/use" means a use, a building or structure, part of a building or structure which is subordinate to, and the use of which is incidental to, that of the main building, structure or use on the same lot. If an accessory building is attached to the main building or structure by a common wall or roof, such accessory building shall be considered as part of the main building. (Ord. 523 § 1(part), 1989)