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Cleaning Roofs

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HI05651703
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If you live in a coastal region or on heavily wooded property, your asphalt roof may have discolored staining from mildew and algae growth. Provided these are just stains and not fungi or mold growth (signs of more serious moisture problems), you can remove the stains easily and have your roof looking new again. The process involves spraying the shingles with a solution of pool chlorine and liquid detergent, then rinsing it off with a garden hose. Chlorine will begin to kill the algae immediately and brighten the shingle color, but it will also continue to work for days after treating. Spray water onto shrubbery and the surrounding yard first, especially in downspout areas, to help dilute the chemical runoff. Use extreme caution when walking on a wet roof. Wear soft-soled rubber sneakers for optimal traction, and protect yourself from the chlorine by wearing a rain suit and safety glasses. Choose a calm, overcast day for the job. If your roof has a steep pitch, do not attempt this project; hire a professional roof-cleaning service to do the work instead.

How to Clean an Asphalt Roof

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    Combine 1 gal. of swimming pool chlorine and 1 oz. of liquid dish detergent in a pump-style garden sprayer. Wear chemical gloves and safety glasses to protect yourself.


    TIP: Spray your shrubs and yard with water to dilute any chemical overspray.

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    Working from the ridge to the eaves, apply the bleach solution with a garden sprayer in 6- to 10-ft. sections. Work quickly so the entire section can be rinsed clean while the treatment is still wet. Wear protective clothing, rubber-soled shoes, and safety glasses when working with the chemical spray.

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    Do not use a pressure washer for this step—it will blast granules off the shingles and shorten their life. Watch your step when working near the eaves. Follow up the first chemical spray and wash with a second application of a 50/50 mixture of chlorine and water. Rinse off the second treatment thoroughly with more fresh water before the chlorine dries.

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