How to Clean Mold off Roof Shingles

Mold stains form on roof shingles where part of the roof is in permanent shade. The mold can discolor your roof and can damage your shingles over a period of time. You can clean the mold off with a basic household bleach, as shown below.

Protect Your Yard Plants and Lawn

Splash your yard plants and lawn around the house with water to prevent harm from the bleach solution.

Make and Apply the Bleach Solution

In a 2 gallon bucket, mix up a cleanser composed of 1/4 chlorine bleach and 3/4 water, and add 1 tbsp. trisodium phosphate (TSP). Using a handheld pump sprayer, apply this cleanser to the moldy shingles only, while wearing rubber gloves.

Check for Cleanliness and Rinse

Allow the solution to soak into the shingles for 15 minutes. Rinse the shingles thoroughly with a garden hose at low pressure. Start from the top shingle and rinse downward to prevent water seepage. Run your gloved hand over the shingles to check for any slimy mold remaining. If some mold remains, apply the cleanser again, wait 10 more minutes and repeat the rinse process.

Precaution

Never use a pressure washer to wash or rinse shingles. It will scrape off the small pebbles atop the shingles and reduce their water repellency.