--75.187.xx.xx

Well, it's a sign that the roof needs cleaning. --50.45.xxx.xxx

If your tires get all muddy after driving it into mud, do you get new tires? --99.59.x.xxx

I wonder what the best wY to clean it would be. Once you get it off the roof I would think the best way to keep it from coming back would be to thin out trees so it gets plenty of sun on the roof? Interesting problem. --174.233.xxx.xxx

It's a sign that it doesn't dry well enough. You need zinc strip. Install it about 3-4 rows down from the peak and when it rains, it will wash zinc down over top of your shingles and keep the moss from growing. --50.32.xxx.xxx

It is a sign of the lengthy humid periods in your area, while the climate has been draining endlessly in central PA and NY we in OH have been hanging onto high moisture for 7 weeks non stop. --76.188.xxx.xx

There is a product called wet and forget. About $20 at Home Depot, and you literally just use the garden hose and wet it down, and it cleans itself over time. --174.232.xxx.xx

There are solutions to wash it with, Wet and Forget is one that is easy, it takes a while but you don't have to do much. There are people to hire that will clean it. Roof shampoo in our area. Zinc strips help to keep it from coming back. --108.44.xx.xxx

I have moss and lichen all over the north side of my house. The roof is 25 year dimensional and it's fine. Moss doesn't have roots that go into the shingles. It's not like ivy which will put holders right into wood or anything else. It's only on the surface. The conditions that allow the moss to grow might mess with your roof under the shingles if there are leaks. --73.178.xxx.xx

Hire a company to power wash it. They can put an algae inhibitor chemical in the wash to clean it and kill it. But you should trim some branches to get more sun on the roof. --108.69.xxx.xxx

Bleach. --184.53.x.xx