What are indicators that a roof may have experienced ponding?

The presence of dirt, algae, and vegetation on the roof surface serves as clear indicators that a roof may have experienced ponding. This accumulation typically occurs in areas where water collects rather than draining efficiently. When water remains stagnant, it creates an environment conducive to the growth of algae and moss, as well as the accumulation of dirt. The combination of these elements signifies that there is a persistent water issue, which could lead to further damage if not addressed.

While vegetation and moss, as well as dirt and algae alone, are relevant indicators, the comprehensive assessment provided in the correct answer encompasses all these factors, presenting a more complete picture of the situation. Additionally, the slope of the roof is important for proper drainage, but it does not directly indicate ponding without considering the resulting effects like vegetation and algae.