Asked on Oct 4, 2017

How to clean and prevent moss on asphalt shingle roof?

Lynne WebbWilliamJoy30150932


5 answers
  • Janet Pizaro
    on Oct 4, 2017

    Use Wet and Forget
  • Johnavallance82
    on Oct 4, 2017

    Sealer coat............
  • Joy30150932
    on Oct 4, 2017

    Some say a zinc strip at the top helps. When it rains the oxide runs down and is supposed to stop the process.
  • William
    on Oct 4, 2017

    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.
  • Lynne Webb
    on Oct 7, 2017

    I dealt with that for years. You must have lots of shade. I have heard, and read, that copper strips strategically placed under and around the shingles will eliminate the moss. Do some research and ask a roofer you trust. Using a bleach solution will kill it for sure but I never had the nerve to put bleach on my shingles.
Your comment...