Any portion of the roof structure above that which is used in measuring the height of a building as defined in §
365-7 as well as penthouses or roof structures for the housing of elevators, stairways, tanks, ventilating fans, air-conditioning equipment or similar equipment required to operate and maintain the building, and fire or parapet walls, skylights, towers, spires, cupolas, steeples, flagpoles, chimneys, smokestacks, monuments, water tanks, silos or similar structures may be erected above the height limits prescribed by this chapter but in no case more than 25% more than the maximum height permitted in the district, except that spires, steeples, silos, water towers and radio and television towers shall not exceed 50 feet in height above the ground level. In addition, all structures are subject to regulations of the Federal Aviation Agency.