Denver Roofing: Article About Removing Roof Stains
Occasionally, black spots may begin to form on asphalt shingle roofs. Some homeowners tend to not worry about these spots; others simply do not know what causes the black spots to form or how to permanently get rid of them. The good news is that these spots are most likely not mold, which can cause the shingles to rapidly disintegrate. The spots are most likely caused by an algae called Gloecapsa magma.
This type of algae can travel from rooftop to rooftop through the air. It feeds on the calcium carbonate that is often contained in asphalt shingles. For the most part, the algae streaks are simply aesthetic; over time, however, the algae can harbor moisture that can eventually cause the shingles to disintegrate. Because the algae can reduce the roof's lifespan and the value of the home, it is recommended that a Denver roofing contractor remove the streaks.
Some homeowners like to use household bleach and a power washer to remove the black stains. This is not recommended because the power washer can destroy the shingles even when it is used on the lowest setting. Additionally, bleach can further corrode the asphalt. An expert roofer will most likely use sodium hydroxide products. Not only do these products work better overall on cleaning up the spots, they are also much less harmful to other vegetation, such as the bushes and flowers used to increase the home's curb appeal.
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Once the roofer is on site, they will first spray the roof with water to reduce the amount of heat coming off the shingles. This prevents the cleaner from simply evaporating when it is applied. Once the solution is properly diluted, a pump sprayer will be used to apply the cleaner. After about 20 minutes or so, the solution will be rinsed off the roof. A special rinsing tool that provides more pressure may be used if the spots are particularly dark.
While these cleaners will remove any black spots that have formed, they will not keep algae from growing. An expert roofer can always incorporate algae cleaning during a routine roof inspection; however, there may also be other options available depending on the age of the roof and the climate. Copper or zinc strips, which can be installed along the roof ridge, are a popular method for keeping algae growth at bay. Otherwise, a stain blocking solution, which provides about three years of protection, may also be used. Homeowners should discuss their options with an expert roofer.