Height. The height limitations of this chapter shall not apply to church spires, belfries, cupolas and domes not used for human occupancy, nor to chimneys, ventilators, skylights, water tanks, similar features and necessary mechanical appurtenances usually carried above the roofline. Such features, however, shall be erected only to such height as is necessary to accomplish the purpose they are to serve. The provisions of this chapter shall not apply to prevent the erection above the building height limit of a parapet wall or cornice for ornamentation (and without windows) extending above such height limit not more than five feet. Public and quasi-public buildings, schools, churches and other similar permitted uses shall increase the front, rear and side yards by one foot for each foot by which such building exceeds the height limit herein established for such zone in which it is located, and further provided that in no case shall any building have a height greater than 50 feet, unless explicitly permitted by the schedule of this chapter.