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How to remove and prevent black algae stains from your bay area roof

Posted on: April 25, 2017

Nobody likes to look up at the roof of their beautiful home or building and stare at dark, black streaky stains. The cause of these eye sores is often attributed to mold, or just dirt. However, the true cause of most of these dark stains is actually a blue green algae, which is spread by airborne spores. These algae colonies feed on both moisture and the limestone filler that is in your asphalt shingles on your roof.

To treat these stains you can call professional cleaners to make sure the right products and techniques are used to care for your bay area roof. If you are looking to save a couple bucks, then, you might be interested in these tips for cleaning your roof yourself.

1) Make sure you have the right chemicals

There are plenty of cleaning products sold by various companies that have a combination of chemicals that are specifically made for roof cleaning and protection. Many people make the mistake of going straight to a chlorine bleach cleaning agent. This method is not recommended because the chlorine bleach is corrosive and will leave your shingles looking significantly discolored. Not to mention the fact that while bleach will kill the surface algae, it does not sink deep enough to eliminate the algae colonies altogether, so you will see the stains return fairly quickly.

2) Prepare the area

Preferably, you should choose a somewhat overcast, but not windy day to clean your roof. Wind can blow your spray from your roof to the neighbors and if it is too hot the water might evaporate too quickly before it has a chance to sink deep down into the algae colonies. Prepare your roof by removing any stray leaves, sticks, or dirt. Then, you will want to repair any damaged or loose shingles and clean out your gutters so that the spray can drain freely.

3) Spraying the shingles

First, you will want to spray down your shingles with just water to cool down your roof and prepare them for the cleaning spray. Once they are fresh and ready you will want to mix your cleaning solution and water at a 1:7 ratio. Using a pump sprayer you are then ready to spray down all of your shingles. You will want to apply your cleaning solution evenly across the stains and other shingles. Be careful while spraying on top of your roof as the shingles will be wet and slippery. We suggest using a full body harness and tying it down to the roof to secure your safety.

After your shingles are evenly coated with your cleaning solution you are going to want to rinse it off with water. A garden hose sprayer should work well for this step. Make sure that you rinse evenly and slowly, so that you are not left with any streaks.

4) Preventing future algae growth

There are many different algae prevention solutions available that you can buy and spray on after a thorough rinse. These products will likely buy you up to three years of growth prevention. Another option is installing metallic zinc or copper strips along the ridge of your roof. These are designed to spread algae killing ions across your roof as it rains. Although these products do not protect against algae growth from humidity, they are better than no prevention.

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