Moss On The Roof Is Charming, But A Sure Fire Way To Shorten The Life Of Your Roof.
It starts with black or green algae about five years after installation--sooner if the roof is under a canopy of trees and doesn't get direct sunlight. A few years later you start to see lichens taking root and then shortly thereafter, moss. Lichens and moss retain water and their roots climb up in between the shingles, separating them, and causing water intrusion. In a cold climate, the water retained in the moss and lichens freezes and thaws, damaging the roof even more and shortening its life. A simple solution to prevent this problem is to "softwash" the roof every 5 or so years with algicide to kill the living organisms. For a cedar shingle roof, you can then follow with a fine spray of tung, or linseed oil to preserve the wood. Not only will your roof look better, but it will last many years longer.


