Moss can grow on roof surfaces that don’t get much sunlight, especially in cool, moist climates. While moss growth can be a cosmetic issue, it can hold moisture against the roof surface and over time in freezing climates can cause damage to the granules on the top of the shingles. Moss can be brushed off but it won’t prevent it from growing again and brushing it from the surface can damage the top of the shingle. Plus, great care should be taken when using a ladder or walking on your roof. You may need to call a professional.
Each of the issues above are signs you may need a new shingle roof. Many times, the solution is as simple as installing new roof shingles, but if you wait too long, you could face replacing some of the plywood underneath. By regularly maintaining your roof, you not only extend its life, but you also set yourself up to see the early signs of a failing roof and get it replaced before you face any water damage or other problems.