If you’ve noticed black streaks or greenish stains creeping across your roof this summer, you’re not alone. Many homeowners in Middletown, NJ are surprised to learn that summer’s strong sun and high humidity actually fuel algae and moss growth on roofs — not burn it away.
Let’s explore why this happens, what those dark streaks really are, and how to protect your roof before it’s too late.
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What Are Those Black Streaks on My Roof?
Those dark, streaky stains aren’t just dirt — they’re a type of algae called Gloeocapsa magma. This cyanobacteria thrives in humid conditions, clinging to roofing materials (especially asphalt shingles with limestone filler) and feeding off the nutrients there.
On top of that, you might see:
- Moss — soft, green patches that trap moisture
- Lichen — crusty, white or greenish growths that break down shingles over time
These organisms don’t just hurt your home’s appearance — they damage your roof’s lifespan.
Read how these organic growths affect your roof overtime.
Why Does Summer Make Algae Growth Worse?
✅ Heat + Humidity = Perfect Conditions
Summer’s high temperatures combined with humid air create a moisture-rich environment where algae and moss thrive.
✅ Shaded, Damp Areas Stay Wet
Roof sections facing north or covered by trees get less direct sun, staying damp longer — perfect for algae spores to grow.
✅ Longer Days, More Sunlight
Ironically, longer sunlight hours don’t kill algae; they warm surfaces, increasing condensation cycles at night.
Common Summer Roof Algae Questions
What causes algae to grow on roofs?
Moisture, limestone in shingles, shade, and airborne spores all contribute to algae growth.
Does sunlight kill roof algae?
Not really — while UV rays can dry surfaces, shaded or north-facing areas remain cool and damp, allowing algae to thrive.
How can I prevent black streaks on my roof?
Regular roof cleaning by professionals removes algae before it causes permanent damage.
Why You Should Act Now
Ignoring roof algae can lead to:
- Premature shingle wear
- Moisture retention and wood rot
- Increased energy costs (due to less roof reflectivity)
- Lower curb appeal and home value
At Power Wash Plus, we use a safe, soft-wash process to remove algae, moss, and lichen without damaging your roof. Plus, we apply preventative treatments to slow regrowth.
Protect Your Roof This Summer — Call Power Wash Plus!
If you’re seeing black streaks or moss patches, don’t wait. Call Power Wash Plus at 732-671-6767, visit our website, or check out our Google Maps listing to schedule professional roof cleaning.
Let’s keep your roof strong, clean, and algae-free all summer long!