The height limitations of this chapter shall not apply to church spires, belfries, cupolas, penthouses, masts and domes not used for human occupancy, nor to chimneys, ventilators, skylights, water tanks, bulkheads and similar features and the necessary mechanical appurtenances usually carried above the roof level. Such features, however, shall be erected only to such height as necessary to accomplish the purpose they are to serve.
Parapet walls, cornices and other ornamental structures extending not more than five feet above the roof shall be exempt from the height limitations of this chapter.