Why Do Shingles Streak?

What are the Black Streaks and Spots on my roof? Answer:

Algae typically known as Gloeocapsa Magma and Blue Green Algae. The reason for the black color is the algae has the ability to form a protective coating (black in color) that shields it from the sun’s harmful rays. This type of algae is most common with asphalt shingles.

How does this happen? Answer:

The wind primarily. The algae spores are air born and are easily transferred from house to house in a neighborhood. The thing is, they’re not just ugly, they are actually Eating Your Roof! That’s right Ladies and Gentlemen, they are eating the “Filler” that’s in the shingle, Crushed Limestone and Fiberglass.

What can I do? Answer:

A simple roof cleaning consisting of Trisodium Phosphate, Bleach and Water will kill the algae.

Will it come back? Answer:

Yes. Usually within a couple of years.

Can I prevent its return? Answer:

If your roof is in good condition you can install a copper strip along/near the “Peak” or top of your roof. Each time it rains the water will wash across the metal (which has properties which inhibit further growth) and run down the roof helping to stop growth.

Is this 100 percent? Answer:

No. But it will offer extra protection. The spores will still feed off of moisture and humidity.

Good News!

The major players in shingle manufacturing are doing their best to catch up by adding copper to their shingles. Example; The Landmark Pro by CertainTeed has a 15year algae resistance warranty. Atlas has taken it a step further and now offers Lifetime algae protection. It’s just a matter of time until they all follow suit.


If you have a roof, A-Plus does it! Shingle, Slate, Shake, Metal, and Flat Roofs of every type, we do it all! Service? We do that too!

Leave it to the pro’s, for all your roofing and re-roofing needs call the professionals at A-Plus Roofing!

By; Doug Pritchard

A-Plus Roofing

© 2023 A Plus Roofing | All Rights Reserved

Powered by Emerge