Granules are the crushed, ceramic-coated mineral particles pressed into the top surface of every asphalt shingle. They're easy to dismiss as decoration, but they're the hardest-working part of the shingle: they block ultraviolet light that would otherwise dry out and crack the asphalt beneath, they shield it from rain and hail, they contribute to the assembly's Class A fire rating, and they give the roof its color. Some lines add copper-bearing granules for algae resistance — see algae-resistant shingles.
Why granules matter in the Umpqua Valley
Our climate attacks shingles from both ends: 130-plus days of rain from October to May, then bone-dry summers with highs in the mid-80s hammering the roof with UV. The granule layer is what stands between that cycle and the asphalt. It's also why moss is such a menace here — moss rhizoids anchor between granules and pry them loose, and why we tell every customer never to pressure wash a roof: one afternoon with a pressure washer can strip years of protection. Our moss prevention guide covers the safe alternative, and our moss removal service exists precisely to clean roofs without sacrificing granules.
When granules go, what it costs you
Granule loss is how asphalt roofs die. Bald spots turn shiny black, the exposed asphalt gets brittle, shingles crack and curl, and leaks follow. Once loss is widespread, there's no restoring it — you're on the road to replacement. Catching localized loss early (one slope, one storm-scoured patch) sometimes allows targeted repair instead.
Should I worry about granules in my gutters?
New roofs shed harmless factory excess. On a 15-plus-year-old roof, though, heavy granule buildup in gutters is an honest early-warning sign — worth a professional look before the next wet season.
Related terms
Algae-resistant shingles · Architectural shingle · Three-tab shingle · Class A fire rating · Underlayment