"Building or structure" means as defined by the building code of the city and also includes retaining walls, stairways, required off-street parking facilities, any well, whether for water, oil or other hydrocarbon products and any underground storage facilities in excess of one thousand gallons capacity; provided, "building or structure" does not include any building or structure as herein defined existing on the effective date of the ordinance codified in this chapter, or trees, agricultural crops, temporary off-street parking facilities not required by the city, walks or public utilities installed under authority of franchise. (Ord. 597 NCS §21.53; prior code §21.53.)