Power-washing your roof is an easy do-it-yourself project to get rid of stains, mold and fungus, but if you are uncomfortable climbing on your roof or don't want to buy or rent the washer, there are numerous companies that will be happy to clean it for you.

Why Power-wash a Roof

Power-washing your roof removes unsightly stains and potentially damaging mold and fungus, increasing your roof's life span. A roof should be power-washed every three to four years, more often if your house is in a hot and humid climate, where mold and fungus are much more likely to grow. Mold and fungus can damage or destroy shingles. Never wash your roof when freezing weather is possible. The freezing water could damage it.

What Equipment to Use

You will need a pressure washer that is capable of spraying water at a force of about 2,000 pounds per square inch, a moderate intensity. The spray nozzle should be 15 degrees--the arc size of the water stream. A 15-degree nozzle produces a tight, fan-shaped arc that works almost like a scraper on fungus and mold and is easy to control. Use a cleaner specifically designed for roofs. Look for one that does not contain bleach, because the runoff could streak and discolor your siding. Wear the proper protective gear: gloves, safety glasses and clothing that completely covers your arms and legs. There will be spray back, so wear water-resistant clothing if you don't want to get wet.

Preparation

Prune back any branches that extend onto the roof. The roof should get as much sunlight as possible, mitigating the conditions that promote the growth of mold and fungus. This is also a good time to clean out the gutters, which will allow the water to drain away quickly. Wash a small section of the roof to test the equipment and cleaner and make sure they do not damage or discolor your roofing material.

Cleaning the Roof

Start from the peak of the roof and work your way down to the gutters. Keep the nozzle at a 45-degree angle and 10 to 12 inches from the surface to reduce the risk of damage to the roof. Clean the roof with detergent on the first power-wash application and rinse it with fresh water on the second. But do the roof in sections so you can rinse 10 to 15 minutes after cleaning and keep the detergent from drying. Use a scrub brush on stubborn stains.

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Power-washing a Roof