Professional Roof Cleaners Association

Asphalt

AsphaltRoof PRCA

What is Asphalt Roof Cleaning?

Roof cleaning originated from the growth of organisms forming colonies on the surfaces of roofs. While most surfaces can get washed clean from rains, some surfaces like roofing materials, prove to be ideal as a breeding ground for organic growths. Most common kinds of growth are Algae, Lichen and Moss. These types of organisms have been persistent in the southern regions of the U.S. and now have expanded to most of the U.S and Canada, leaving the driest regions out. All three are moisture-loving growths and capable of retaining moisture while adhered to any surface.They are proven to withstand antarctic conditions and droughts.

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Normal Asphalt Roof Mat
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Over Growth of Lichen on Roof
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Microscopic View of Lichen On Roof
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What Color is Your Roof?
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Algae and Lichen
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Lichen damaged Asphalt Roof
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Lichen Roof Damage
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Where do these growths on the roof come from?

The black stains are algae. They usually will be heavier towards the bottom and taper up, as they get closer to the ridge. Algae and other growths on the roof spread from one infected roof to another. This airborne algae will land on any surface as it is blown by winds or carried by animals. Once the spores make it to the roof, they will begin to accumulate, first typically showing up on the north and most shady sections of the roof.

The reason the roof looks like it is dirty with black streaks is because this type of algae has a protective cover. This cover is what gives it the black color as well as protection from UV rays. The algae growth starts slowly and will accelerate from the rainy seasons. This is why you may have only recently noticed its appearance. Once the algae starts, the lichen and moss will soon follow and that is where the more extensive damage will begin. These three support each other within the environment and will usually be found co-existing on most roofs. Most of the time consumers are unaware that the lichen and moss are present until the roof has been cleaned. Lichen and moss will turn white from the roof cleaning application. They blend in very well and unless you walk your roof and inspect the shingles, they are not visible from the ground. You can see them growing on the tree trunks surrounding your  property. This maybe a pretty good precursor to your roof’s condition.

Why should a roof be cleaned?

The answer is varied and can really be answered in accordance with the geographical location of your property. Many homeowners throughout the US get letters to comply with homeowners associations to keep the neighborhoods looking esthetically pleasing.

Roof cleaning is a sound choice to extend the lifespan of a roof system. The build-up of algae, lichen and moss will damage your asphalt shingles, which will end up in a premature roof replacement. The Asphalt Roof Manufactures Association (ARMA) highly recommends cleaning and maintaining your roof system. The choice to maintain your roof’s surface should be an important and informed decision. Left untreated, the shingles will only accumulate more growth and retain moisture. A roof that retains moisture is a roof that will eventually fail, far before its life expectancy. Shingle roofs will deteriorate due to decomposition from the excessive moisture and the inability to completely dry out. The valley’s are especially vulnerable due to the channeling of the rain waters. In essence roof valleys are the initial breeding ground for the organisms.

The process for cleaning shingles.

PRCA supports and recommends the same cleaning process that is highly recommended by ARMA, NRCA and all shingle manufacturers. They have researched, studied and written the proper cleaning policy’s. These authoritative associations have clearly stated “DO NOT power wash a shingle roof “with any kind of equipment attached to a power washer. PRCA members use these recommended procedures (non-pressure) and chemicals that the shingle manufacturers recommend. Make sure the contractor chosen to clean a roof will be using the non-pressure process. Ask the most important question. Will you use a pressure washer on my roof?” Be careful of the answer. You can hear all kinds of low-pressure answers. Even the lowest setting on a pressure washer will cause damage to the shingles, which will not give the roof the added value of extending the life of your roof and could void your existing warranty.

Who is ARMA?

ARMA is the professional collaboration of major roof manufacturers like GAF, IKO, Certainteed, Tamko,Pabco and Owens Corning. They also include the suppliers of raw materials to these corporations like 3M whom manufactures the granules used within the production plants.

AsphaltRoofing.org

Who is NRCA?

National Roofing Contractors Association is a professional industry that leads the voice for various contractors throughout the United States and works with manufacturers to improve the industry as a whole.

NRCA