The height limitations of this chapter shall not apply to church spires, belfries, cupolas, penthouses or domes not used for human occupancy, nor to chimneys, ventilators, skylights, water tanks, silos, parapet walls, cornices without windows, antennas, necessary mechanical appurtenances usually carried above the roof level or to public buildings or structures located more than one foot horizontally from the property line for each foot of building height.
(`92 Code, § 40-4-15)