How do I remove moss from my roof?

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  • William William on Jan 28, 2019

    The black mold-like stains and streaks that appear on roofs, particularly light-colored asphalt shingles, is actually a blue-green algae (Gloeocapsa magma). Commonly found in climates with warm, humid summers, it does no damage to the roofing, but it certainly does looks bad.


    The less expensive solution is to spray wash the roof with a 50 percent mix of water and bleach to get rid of the algae. (No pressure washers, please. They're likely to damage the shingles.) Just be sure to wet your foundation plantings first, and rinse everything in clean water when you're done. Plants don't like bleach, and wetting them with plain water first protects them. You can also cover them with tarps or plastic sheeting, which will protect the soil around your plants as well. Make sure that you create a wide radius around your home to be safe.

    Allow the solution to soak into the shingles for at least 15 minutes. If they are severely molded, you may want to give it a little longer. Next, rinse the shingles thoroughly with a garden hose at low pressure. Start from the top shingle and rinse downward to prevent water seepage.


    To keep the algae from coming back, insert 6-inch-wide strips of zinc or copper under the row of shingling closest to the roof peak, leaving an inch or two of the lower edge exposed to the weather. That way whenever it rains, some of the metal molecules will wash down the roof and kill any algae trying to regain a foothold on your shingles.

    You can probably see this same principle working on roofs in your neighborhood. Look for chimneys with copper flashing; the areas directly below the flashing will be free of any algae stains.

    The strips also work on roofs suffering from moss buildup. Just scrub it off first with a brush, then bleach as above.

    • Fran Fran on Jan 30, 2019

      Dear William. Thanks so much for your very intense solution to the moss problem on my roof. I go appreciate you taking the time to write such a great reply. It’s odd that this is the first year I’ve had this issue as I’ve lived in my house for 20 years. Again thanks so much

  • Oliva Oliva on Jan 28, 2019

    Depending upon the height of your roof, you can purchase Wet n" Forget Outdoor spray, when can be applied with a garden sprayer, to your roof, on an overcast day. Saturate the area. It will take some time, but does work. You can see videos at the Wet n' Forget website.

  • Fran Fran on Jan 28, 2019

    Thank you for your response. Now I have to find someone to climb on the roof and do this for me!!

    • Fran Fran on Jan 30, 2019

      Great idea about the insurance!!

  • Judy Judy on Jan 29, 2019

    The reason for the moss is lack of light and air circulation. Is there a tree or something over the roof?

    • Fran Fran on Jan 30, 2019

      Not on the front of house but it dies face North however I’ve lived here 20 years and this is the first year it happened. 🤔