Asphalt roof cleaning is the removal of organisms, such as algae, lichen, and moss from asphalt shingles. While many surfaces can be easily cleaned with a good rain shower, most roofing materials require a more in depth cleaning process to remove these organisms and prevent the growth of large colonies. Algae, lichen, and moss growth on asphalt shingles is most common in the Southern region of the United States, but can be found throughout the U.S. and Canada. They thrive in moisture rich areas, but have been known to withstand antarctic conditions and droughts.
Have you noticed black stains on your asphalt roof? These stains are usually heavier toward the bottom and taper up as they near the roof ridge. These black stains are evidence of algae. The reason the roof appears dirty with black streaks is because the algae has a protective cover, giving it a black color and protection from UV rays.
Asphalt roof cleaning is a sound choice in extending the lifespan of your roof. The build-up of algae, lichen and moss will damage your asphalt shingles, resulting in an early roof replacement. The Asphalt Roof Manufactures Association (ARMA) highly recommends regular cleaning and maintenance of your roof. The choice to maintain your roof’s surface should be an important and informed decision. If left untreated, the shingles will accumulate more organic growth and retain excessive moisture, causing deterioration and decomposition. The valleys of your roof are especially vulnerable to deterioration due to the channeling of rain water, creating a breeding ground for the organisms. Essentially, a roof that retains moisture is a roof that will eventually fail.
PRCA supports and recommends the same cleaning process that is suggested by the Asphalt Roof Manufacturers Association (ARMA), the National Roofing Contractors Association (NRCA), and all shingle manufacturers. These authoritative associations have studied and researched proper asphalt cleaning procedures. They clearly state that a roof cleaner should not power wash a shingle roof with any kind of equipment attached to a power washer. PRCA members use the recommended non-pressure washing procedures and chemicals that the shingle manufacturers recommend. Make sure that the contractor you choose uses the non-pressure process. Ask them the most important question: Will you use a pressure washer on my roof? Pay close attention to their answer, specifically low-pressure answers. Even the lowest setting on a pressure washer will cause damage to the shingles. It will not extend the life of your roof and could void your existing warranty.