The climate has a lot to do with mold and algae formation on roofs, which is why homes that have asphalt shingles roof are most vulnerable to mold growth that occurs due to wet and humid conditions prevailing for a long time. Algae growth leads to molds as also moss and lichens, which can damage the roof surface and reduce its longevity. The rainy season aggravates mold growth, but even when it is not raining, hot, humid, and moist climate is most conducive for botanical growth on roofs that thrive in shady conditions. Areas of the roof that remain under the shade of trees or surrounding buildings for most of the day are most prone to mold growth.

Removing mold or any other type of botanical growth from the roof should be a priority because it does not remain restricted on the roof only but can pass into the home indoors when washed away by rainwater. This can multiply the problems due to the health hazards posed to the residents.

Any roofing contractor can clean mold and algae from the roof by using any of the following techniques.

By using chlorine bleach solution

Cleaning mold from the roof is a 4-step process. 

  • Before you begin the process, spray adequate water on the plants that grow around your house to protect it from the spillage of chlorinated solution that can damage the plants.  

 

  • Prepare a solution by mixing one-part bleach to three parts water and use a hand sprayer to spray the solution on the mold and mildew affected areas of the roof. To make the removal process more effective, you can add some tri-sodium phosphate to the solution that acts as a cleanser and will clean the roof at the same time.

 

  • After spraying the solution, allow it to remain in place for 15 minutes and then water it down with a hose and rinse it off. If there are some traces of mold and mildew sticking to the roof, which you can make out from the slippery feeling on rubbing your hand against the surface, then you need to repeat the process.

 

  • Finally, rinse the roof with water to remove any trace of chlorinated bleach that can damage the roof.

By using a copper sulfate solution

The steps of mold removal by using copper sulfate solution are the same as above and to prepare the solution mix 12 ounces of dry copper sulfate to 1 gallon of warm water.  After applying the solution to the affected areas, wait for 15 minutes and then sweep off the loosely clinging mildew with a broom. In the end, wash the roof with water and rinse it off.

Prevent mildew formation

Since mold and mildew thrive in shady conditions, you must remove the overhanging tree branches to allow air and adequate sunshine on the roof. Changing the environment will deter mold growth and stop it altogether. 

Installing zinc strips near the ridge of the roof and under a row of shingles will prevent mildew formation. When rainwater soaks the zinc strips, it forms a solution that slows down the growth of mildew and mold.