When the shingles’ protective top layer of granule coating begins shedding off into the gutters. This coating functions as a sort of “sunscreen” for your shingles. The oil contained within the shingles is essential for maintaining this coating, but as it dries out, the shingles will start to become brittle and crack.
Black stains and streaks on the shingles is another sign that the roof is aging. Most roofs with staining are shedding the protective top coating to varying degrees. Note: Staining does not harm the roof and is only an aesthetic issue.