Cleaning, repairing, and treating your cedar roof with a water based preservative every 5 to 6 years will double your roofs remaining years of useful life. The cedar oil in cedar shakes offers strong protection from the weather, moss, and fungus. Once this oil has leached out of the outer layers of the shakes this leave the shake susceptible to curling form the sun, and moss growth on the north side, and tree covered areas of the roof.
The water based preservative that we use (STA-BRITE) contains UV blockers to stop the shakes from curling, and moss and fungus inhibitors. Most importantly, the preservative will make the roof water repellent. Areas that do not dry properly after rain events will now dry quickly, and eliminate the growth of moss, which needs a wet roof to germinate.