The dark stains streaking your shingle roof are likely to be the result of a species of bacteria. They may be harmless to you, but the same is not true of your roof in the long term. In the interim they may lower the perceived value of your home.

Bacteria on My Roof – That Sounds Gross

The offending bacteria, gloeocapsa magma are a subspecies of an ancient line of photosynthesizing bacteria. They decompose water releasing oxygen gas, and become evident as they assume their dark, hard UV-protective outer coating. There are several reasons for their increasing prevalence since the 1990’s.

The Three Main Reasons for the Dark Stains Streaking Your Roof

1… Climate change resulting from global warming is increasing humidity and temperature allowing the bacteria to thrive

2… Fibreglass shingles, with limestone filler inside the asphalt contain moisture and are ‘bacteria food’

3… The air born bacteria arrive on your roof, enjoy a quick snack, and then settle down in your hospitable environment

Should I Worry About the Dark Stains on My Roof?

Limestone is food to gloeocapsa magma bacteria. They consume the limestone granules embedded in the asphalt. This decreases the shingles’ ability to reflect ultra-violet light and shortens their lifespan.

This may in turn lead to earlier roof replacement, lower property value, and even a voided insurance policy. HVAC cooling costs may also increase as the damaged roof admits more solar heat.

Is There a Way to Get Rid of the Infestation?

The dark stains streaking your shingle roof are warning signs of growing bacteria colonies. They migrated across from a nearby roof in the wind, and you won’t get rid of them permanently. You can, however mitigate the damage with regular cleaning.

We’ve heard the Asphalt Roofing Manufacturers Association recommends applying a 50 / 50 mix of chlorine bleach and water. However, since chlorine is corrosive we recommend the following precautions:

1… Be careful working on a roof because of the dangers of falling

2… Check your personal accident policy for any restrictions

3… Be mindful that wet roofs are slippery when up there

4… Wear rubber gloves and eye protection without exception

5… Rinse off after 20 minutes with a low-pressure water spray

Speak to Us for Advice before You Start

We charge reasonable rates for roof cleaning, and we have a contract that protects your interests. Why take chances that could see you off work for a week? Call our friendly help line on (403)829-1661. We’ll stop by, and give you a free quote to remove the dark stains streaking your shingle roof anywhere in Calgary.

More About Asphalt Roofs

How Long Asphalt Shingles Should Last

The Minimum Roof Pitch for Regular Shingles

Gloeocapsa Magma Bacteria on a Shingle Roof: Mc Booz BY CC 3.0