All buildings hereafter erected and existing buildings which may be reconstructed, altered, moved or maintained or enlarged shall comply with the height regulations of the zone in which they may be located. Roof structures for the housing of elevators, stairways, tanks, ventilating fans or similar equipment required to operate and maintain the building and fire or parapet walls, skylights, towers, church spires, flag poles, chimneys, smokestacks, wireless masts or similar structures may be erected above the height limits prescribed in this title; provided, that the same may be safely erected and maintained at such height in view of the surrounding conditions and circumstances, but no roof structures or any space above the height limit shall be allowed for the purpose of providing additional floor space.
(`78 Code, § 17.66.020.)