Roofing systems (especially, flat roofs) take a beating. They are subjected to exceptional weather conditions including UV degradation, excessive heat, extreme cold, high winds, heavy rains, and snow loads just to name a few. Stressed by natural building and structural movement due to settlement. Changes in building usage or the addition / alteration of penetrations

Here’s a great article on Roofing Maintenance from facilitiesnet.com. Source: Regular Roofing Maintenance: When to Inspect the Roof – Facilities Management Roofing Feature