How to Clean Mold Off a Roof

Exposure to mold causes and exacerbates symptoms of several medical conditions, including allergies, irritation of tissues from inhalation or ingestion, and infections. Molds that contain mycotoxins are even more dangerous. Although mold growing on a roof is typically not toxic and does not damage the roof, it is unsightly. Furthermore, too much mold growing in and around your living environment can have cumulative effects on the health of you and your family.


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    Remove surface mold from the roof before you wash by scrubbing it with a hard, short-bristled brush or broom. Long handled brushes, which give you better reach, can be found in most hardware stores.
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    Use a chemical sold commercially for mold removal, or a 50/50 combination of water and bleach to saturate the surface of the roof. The easiest way to do this over a large area is with a yard and garden chemical sprayer filled with the bleach solution.
  3. Image titled Clean Mold Off a Roof Step 3
    Scrub areas with visible mold again using the brush or broom, then give those areas a second spray with the bleach and water mixture.
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    Allow the bleach solution to dry on the roof do not hose or wash it off.


  • When it is time to replace roof shingles, consider replacing them with shingles made with copper granules that inhibit mold growth.
  • Prevent mold from growing on the roof in the future by installing a strip of zinc or copper where mold grows. Place a 6-to-8-inch strip of the metal under the first row of shingling closest to the roof peak. Each time it rains, metal molecules wash down the roof and prevent spores from growing.
  • Mold typically grows on the side of the roof that gets little or no sun. Trees and other plants around your house, as well as proximity to water sources and frequency of rain, also affect mold growth.


  • Water all plants growing within a few yards of the foundation thoroughly before beginning the roof cleaning. If the plants are well watered they are less likely to suck up the bleach or chemical you use when cleaning the roof. After you are done cleaning, water the area thoroughly again to wash any toxic products through the ground and dilute it.
  • Wear rubber gloves whenever you are working with mold. A face mask is also a good idea to block airborne spores.
  • Good shoes or boots with plenty of tread should be worn if reaching the mold requires going out onto the roof. Mold removal is done with wet methods that make the surface of the roof slippery. If possible, do the job standing on a ladder instead.

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Categories: Exterior Walls and Roof