In the greater Seattle are and northwest moss grows all over because of the moisture, especially in shaded areas that are covered by trees or places where there is not a lot of sun. Moss removal and roof cleaning help maintain and keep the life or your roof. Here we have a really steep roof in Seattle that is covered in moss. We brush up to ninety percent of the moss then apply zinc sulfate to kill the rest and keep future moss from growing. With any type of roof cleaning, gutter cleaning is almost a must. To keep moss maintained we recommend applying zinc sulfate to problem areas annually, usually when gutter cleaning is performed we spread moss killer.