Roof Discoloration: Answering FAQs About Blue-Green Algae

The black streaks on roofs are blue-green algae. They shouldn’t be confused with moss, which is similar but looks three-dimensional. While roofs deal with mold, this growth thrives on decking boards and rafters.

Blue-green algae appear dark because of the color of their covering used as protection from ultraviolet light. Although no evidence proves that they’re a structural concern, any Hader roofing expert would say that they’re a definite eyesore. Their darkness could also affect the thermal properties of reflective roofs over time.

To further understand blue-green algae and keep their unsightly discoloration to a minimum, let’s answer the most asked questions about them:

What Causes Them?

Blue-green algae are bacteria that move with the wind. In other words, there’s no escaping them. However, they rely on moisture to live and extract nutrients from airborne dust and crushed limestone in modern asphalt shingles. Considering that, a damp environment is necessary for them to stay alive, they usually proliferate in shaded areas.

How to Treat Them?

A 50/50 solution of water and chlorine bleach should kill algae growth. Waiting for about 20 minutes before rinsing it off should get the job done. Harsher chemicals are usually ill-advised by many manufacturers; usage of such may void your product warranty. The water-bleach solution should impede algae growth for at least a year.

Can They Be Prevented?

Without doing anything more, blue-green algae will surely return. To keep them from coming back, you can install strips of copper or zinc under the row of shingles closest to the ridge. The ion of either metal is lethal to these microscopic pests. When it rains, the zinc or copper molecules will wash down, and exterminate blue-green algae along the way.

If you need a new roof anyway, it’s wise to invest in roofing materials laced with copper granules. Such products can prevent pronounced blue-green algae stains for many years because they release metal ions whenever they get wet.

Turn to a Hader Roofing Specialist to Combat Algae Growth

There’s a Hader roofing remedy to every roofing problem and blue-green algae discoloration isn’t an exception. Call Hader Solutions at (513) 612-9201 or fill out this form to discuss your roofing needs.


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