Most people don't look at their roof until something's wrong. Here are the signs it's time for a cleaning, and why it matters for more than looks.
1. Black streaks running down the roof
This is the most common sign. The streaks are usually algae (Gloeocapsa magma), which spreads by spores and feeds on the limestone filler in asphalt shingles. It starts on the north and shaded slopes and spreads from there.
2. Green or white crusty patches
That's lichen. Lichen attaches tightly to shingles and can damage the surface as it grows. It's slower to release than algae and may take a few rains after cleaning to fully wash away.
3. Moss along shingle edges
Moss holds moisture against the roof and can lift shingle edges, which lets water get underneath. It's most common under trees.
4. Your energy bills or attic feel warmer
Dark growth absorbs heat. A clean roof reflects more sunlight, which can help keep the attic cooler in summer.
5. You're selling, refinancing or renewing insurance
A streaked roof looks older in listing photos and to inspectors than it may actually be.
Why not just pressure wash it?
High pressure strips the granules that protect shingles from UV, which shortens the life of the roof. The safe way is a low-pressure soft wash that kills the growth. Learn how our roof cleaning works.
