Penthouse or 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, steeples, flagpoles, chimneys, smoke stacks, water tanks, wireless or television masts, silos, or similar Structures may be erected above the height limits herein prescribed, but no space above the height limits shall be allowed for the purpose of providing additional floor space, and no heights are permitted above the maximum allowed under applicable Airport Height Provisions. Height shall be measured from the average finished Grade of the Front Yard.