Moss and algae can damage roofs in a few ways. One of the main ways is by trapping moisture against the roof surface. When moss and algae grow on a roof, they hold onto moisture which can cause the roof to rot and deteriorate. The moisture can also seep into the underlying structure of the roof, causing damage to the decking, framing, and insulation.
Another way moss and algae can damage roofs is by breaking down the roofing materials. Moss and algae can cause shingles to become brittle and lose their granules, which can lead to leaks and other issues. They can also cause metal roofs to rust, which can lead to leaks and structural damage.
Finally, moss and algae can cause discoloration on the roof and make it look unsightly. This can decrease the curb appeal of the house.
It is important to note that moss and algae growth is more common in areas with high humidity and rainfall, like Portland OR, so homeowners in those areas should be extra vigilant about cleaning their roofs regularly to prevent moss and algae growth and the damage that it causes.