Hi Karen,

Thank you for your question, moss growing on a roof cover is an indication of excess moisture exposure, which may lead

to moisture related problems to the roof covering and roof structure. Often proximity to trees, poor roof surface drainage, buildup of organic

debris, and absence of sunlight (usually North sides) and adequate surface drying are possible causes. Treatment to remove moss is often

accomplished using materials containing zinc; however establishing cause for moss formation should be undertaken first as

preventive action. A roofing specialist may be required to assess for cause, damage and repairs.