Why Do Roofs Get Black Streaks in Michigan?

Believe it or not, that’s algae! Those streaks are Gloeocapsa Magma, otherwise known as “Blue-green algae”. I know, those streaks aren’t blue or green, they’re black, right? If it was up to me, I’d name it black algae. 

So what causes this black blue-green algae?

Well algae is a plant, so it needs some basic elements such as water. Do we get rain & dew on our roofs in Michigan? Oh yes, we do. Plants also need indirect sunlight. Do these black streaks only appear on the North side of a house? Yeah, hmm.

At this point you may be thinking: “Okay the black streak algae is caused by water & indirect sunlight so there’s no way to prevent it because you can’t stop the sun & clouds.”

The copper solution!

Thanks to our friends at 3M Scotchgard they invented roof shingle granules that are embedded with copper!

Now you’re probably thinking: “Yea so??”

So, Copper is the sworn enemy of algae & the protector of roofs!

Copper kills algae by binding to it, which damages the algae cells, causing them to leak and die.

The International Code Council requires 2% of all shingle granules to be embedded with copper. Obviously, that’s not enough in Michigan!

Make sure the contractors in Lansing, MI, you hire install shingles that have at least 5% copper granules. If you're searching for roofing companies near me, be sure to ask them about their Roofing products. Most shingle manufacturers offer shingles with approximately 2%–5% copper granules, but companies such as Atlas & Malarkey offer up to 10% & 12% copper!

So why in the world would these roofing companies knowingly sell you roofing shingles that will streak black? The conspiracy theorist in me says: planned obsolescence! They may be selling cheap asphalt shingles or low-quality roof shingles comparable to basic Home Depot shingles. However, the reality isn’t as sophisticated. The fact is, most roofing contractors want to give you the lowest bid, which we all know usually means the worst product and the biggest rip-off.

Higher-copper-content shingles may cost you 5% more than the streaking kind, but they will look brand new for decades, until the day you want to sell your home. Think about the resale value.

Resale value. Sounds like another blog may be in the works!

Have a great day, and remember: in home improvement, you can only pick two: cheap, fast, or good!

Community Construction has seen—and fixed—black algae streaks on homes from Okemos to Traverse City. If your roof looks like this, call us at (517) 969-3556.

Frequently Asked Questions regarding Roof Algae in Michigan

• Q: Can I power wash black streaks off my roof?

• A: We do not recommend high-pressure washing as it removes granules. The best solution is preventing it with high-copper shingles like Malarkey or Atlas.

• Q: How long do shingles with copper last?

• A: Quality shingles with 10%+ copper content can remain algae-free for decades.