What is exactly is roof cleaning? And, why should I do it?

Why does my roof have black running down it?

This isn't a failed roof. It just needs to be safely cleaned.

This is how your roof should look

Do you live in Iowa and you're starting to notice your home's roof is getting darker? Or maybe you have ugly black roof stains running down your roof? Don't worry—it’s not your roof’s final days, despite what many contractors might suggest (they’d love to sell you a new one). Those black streaks are caused by Gloeocapsa magma, an algae that starts as airborne spores and thrives when it lands on your roof. It grows because it’s found a food source—limestone—and appears as dark, streaky stains. These streaks are also a perfect breeding ground for lichen growth, compounding the problem.

Why clean your roof?

It’s HUNGRY!

Gloeocapsa magma feeds on limestone, a key component in today’s fiberglass asphalt shingles. Up until the

1980s, shingles were organic, made with heavier cotton textiles. However, to save costs, manufacturers shifted to limestone fillers, which also help reflect UV rays. This made shingles cheaper—but more susceptible to algae growth.

It’s HOT!

Those black streaks absorb heat, breaking down the petroleum-based asphalt and leading to premature shingle failure. A 30-year shingle could become a 15- to 20-year shingle without proper maintenance. Spending a fraction on cleaning now saves thousands on replacement costs later.

Additionally, heat from algae-covered shingles doesn’t just stay on the roof—it radiates into your attic and home. Studies show attic temperatures can spike by up to 60°F higher with full algae coverage. Higher attic temps mean wasted energy and higher cooling costs, especially for bonus rooms or finished rooms over garages (FROG).

It’s UGLY!

Let’s be honest—those stains aren’t pretty! They detract from your home’s curb appeal and may turn off potential buyers. Cleaning your roof not only enhances its appearance but could also save you from price reductions or extra mortgage payments when selling.

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The Big Question:

It’s not “should I clean my roof?” Can you afford NOT to?

Interested in learning more? If you're in Iowa, but outside of our service area of Iowa City, North Liberty, Cedar Rapids, Davenport or any of the small town in between, that's ok, we still want to help. Let’s talk roof cleaning tips and choosing the right professional!