Exceptions to height limitations. The provisions of these regulations with respect to heights shall not apply to church spires, cupolas, grandstands, chimneys, flagpoles, radio aerials, television aerials and their supports, nor, if not occupying an area greater than 25% of the ground area covered by the main building, to domes, ornamental towers, observation towers, water towers, penthouses, hose towers, water tanks and scenery lofts.