The answer to 'why is my asphalt shingles water stains' is that water stains on asphalt shingles are typically caused by a problem with the roof's drainage system or underlying structure. This can be due to issues like clogged gutters, improperly installed flashing, or damaged shingles that allow water to seep through.
The most common symptoms of this issue include dark, discolored streaks or spots on the shingles, which may indicate the presence of moisture. If left untreated, these water stains can lead to further damage, such as mold growth or premature deterioration of the shingles. In many cases, addressing the root cause of the problem is the best solution, which may require cleaning gutters, repairing flashing, or even replacing damaged shingles. For more complex issues, it's generally recommended to call a professional roofing contractor to properly diagnose and resolve the problem.