When should shingles be replaced, and which warning signs matter?
Short answer. Shingles should be replaced when they stop doing their job: when bare asphalt shows through lost granules, when they curl, crack or lose their seal across whole slopes, or when hail has bruised them. Some things that look alarming, like black algae streaks, are mostly cosmetic and do not by themselves mean replacement.
Usually cosmetic
- Black streaks. Algae feeding on limestone filler in the shingles. Unsightly, but not a reason to replace on its own. See black streaks and algae on roofs.
- A few loose granules in the gutters on a newer roof.
- Slight color variation between bundles, visible in certain light.
Watch closely
- Moss and lichen. They hold moisture and lift shingle edges over time. Light growth is manageable; heavy growth shortens roof life.
- Blisters. Small bumps that can pop and leave bare spots, often tied to attic heat.
- Exposed nail heads or nail pops. Repairable, but a pattern suggests poor installation.
Usually means replacement
- Widespread granule loss. Dark, smooth patches on several slopes, with granules piling at downspouts.
- Curling and cupping across a slope, not just one shingle.
- Cracking. Shingles that break when lifted or have split across the tab.
- Lost seal. Tabs that lift freely in wind on many courses.
- Hail bruising. Random dark spots with soft centers and missing granules.
Put it together
One cosmetic issue on a 10-year-old roof is not a replacement. Several functional issues on a 20-year-old roof almost always are. The full replacement checklist is in signs you need a new roof.