(a) Allowable Exceptions. No structure shall be erected or altered to exceed the height limit established for the district in which the building is located. However, the following structure types may exceed the applicable height limits: roof structures which enclose elevators, stairways, tanks, ventilating fans or similar equipment required to operate and maintain the building and fire or parapet walls, skylights, towers, steeples, stage lofts and screens, flagpoles, chimneys, smokestacks, radio and television aerials, wireless masts, water tanks or similar structures.
(b) Height Limits for Exceptions. Radio, television and wireless aerials or masts may be erected to any height. No other such structure shall be erected to exceed by more than fifteen feet the height limits of the district in which it is located, shall have a total area greater than twenty-five percent of the roof area of the building, or shall be used for any residential purpose.