Cedar Shakes need to be cleaned periodically, but you must be cautious because an untrained person can cause serious damage, leakage and erosion on your roof. Experts generally recommend pressure washing and oiling your cedar shakes every 5 years. It is also recommended that oil be spread on newly cleaned cedar shakes for three reasons.
It acts as a natural water repellant, it conditions the wood so that it doesn’t split and cup, and it is fantastic at inhibiting new moss growth. Oiling a cedar shake can be expensive to do, however, the return on investment is very high when evaluating the life of your roof.
Tile Rooftops
If you choose to pressure wash your tile roof, hiring a qualified expert to clean your roof is of critical importance, because if done incorrectly, it can lead to water being forced into the underfelt and timbers where it can eventually touch insulation and electrical fixtures. Anyone caring for your tile roof should understand the intricacies of this type of roof construction.
Composition Roofs can be power washed if you need to get rid of visible moss (as when you’re putting the house on the market, for instance), but this job needs to be done by a professional to avoid destroying “Roof Sand,” which is actually ceramic shavings that have heat-deflecting properties. When you use a power washer with proper care to remove moss, it is no more or less destructive to the roof than any other method that also removes the visible moss.