The answer to 'flat roof water stains' is that they are a common issue caused by a variety of factors, including poor drainage, leaks, and condensation. Water stains on a flat roof can indicate an underlying problem that needs to be addressed.
Some of the most common causes of flat roof water stains include clogged drains, improper installation or sealing, damage to the roof membrane, and issues with the flashing around vents, chimneys, or other roof penetrations. Symptoms can include discoloration, staining, or even visible pooling of water on the roof surface.