You probably already know that using a pressure washer to clean your roof is a very bad idea. There are countless internet resources that will tell you as much. It may be tempting to clean your roof with a pressure washer but it could cause significant damage to your shingles and, in turn, the contents of your home.
Many cleaning companies will remove moss by simply blasting it with a power washer. This is actually a huge detriment to your roof. By removing moss with a power washer, the lifespan of your roof is significantly shortened. Power washing will remove moss from your roof, but it will also remove the asphalt granules from your shingles. This is the stuff that protects your shingles from wear, giving them a longer lifespan.