What Causes the Black Streaks on My Roof?
What Are the Black Streaks on Your Roof?
If you’ve looked up at your roof and noticed long, dark streaks running down the shingles, you’re not alone. These stains are typically caused by a type of blue-green algae known as Gloeocapsa magma. This airborne algae thrives in warm, humid environments and feeds on the limestone filler found in many asphalt shingles.
But algae isn’t the only culprit. Over time, roofs also collect:
Mold and mildew from trapped moisture
Moss and lichen in shaded or damp areas
Debris buildup like leaves, pine needles, and dirt
All of these can create a breeding ground for further biological growth—and serious problems.
Why You Should Be Concerned
While the black streaks may start off as a cosmetic issue, they can quickly evolve into something much more damaging:
Shortened roof lifespan: Algae, moss, and mold hold moisture, causing shingles to deteriorate faster.
Increased energy bills: Dark stains absorb more heat, making your attic and home warmer and less energy-efficient.
Structural damage: Moss roots can lift and separate shingles, allowing water to seep underneath.
Health concerns: Mold spores can travel through vents and impact indoor air quality.
How to Prevent and Remove Roof Stains
The good news? You don’t need a new roof—you need a safe, professional cleaning.
Use a Soft Washing Method
Unlike traditional pressure washing, which can damage shingles and void your roof’s warranty, soft washing uses low pressure and eco-friendly cleaning agents to break down algae, mold, and stains at the root—without harming your roof.
At Next-Gen Wash Pros, our soft washing service:
Gently removes black streaks, moss, and mildew
Kills algae at the source to prevent regrowth
Restores the appearance and extends the life of your roof
Is 100% safe for shingles, landscaping, and pets
Schedule Routine Cleanings
We recommend having your roof professionally cleaned every 1–3 years, depending on tree cover, humidity, and roof material.
Trim Trees and Improve Drainage
Reducing shade and improving water runoff helps keep your roof dry and algae-resistant.