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heavy moss on garage roof

What is Moss?

Moss is a plant species that grows really well in moist cool areas. There are many different species of moss. Some common characteristics among these species are that moss does not have flowers or seeds, they must have a damp environment to grow in because they do not have any root system to secure water, and they are usually extremely green with tiny leafs.

What Promotes Moss Growth?

A shady climate. The climate doesn’t need to be too shady but shade is optimal.  Acidic environments, more specifically moss grows optimally at a pH level of 5.0 to 5.5. Moss grows well on hard surfaces and needs a moist/humid environment to grow.

How to Kill Moss?

Make its Environment Acidic (below pH 4)


There are many common household items that have a pH level at or below 4. These products are highly effective at killing moss. Using these products with a mixture of water or directly to the moss can kill the plant. Be aware that acid products erode certain types of surfaces. By diluting the mixture you can prevent unwanted corrosion.

  • White Distilled Vinegar (Apple Cider Vinegar As Well)
  • Orange Juice
  • Lemon Juice
  • Tomato Juice

Make its Environment a Base (Above pH 7)


Since moss grows in a pH environment of 5.0 – 5.5 or 6.0, by changing the environment to a base level it will effectively kill the moss. Below is a list of some common household items that are bases. By mixing these products with water or by applying them directly they can kill moss in yards, off of roofs, siding, decks, or other unwanted areas.

  • Baking Soda
  • Baking Powder
  • Salt
  • Ammonia
  • Soap
  • Bleach (Do not mix bleach and ammonia)

Warning: How Not To Kill Moss on Roofs


Roofs are an investment that must be safe guarded. That being said, we want to give you some “what not to do” tips when trying to remove moss off of your roof.

pressure washer damage

Do not pressure wash the moss off

By using a pressure washer to remove the moss, you are going to dramatically reduce the life of your roof. How? The high powered water will remove the asphalt shingle granules which help protect the shingles and ensure a longer life span.

Be careful with using acids to remove moss. If your acidic mixture is too strong or stays on the roof too long, it can eat away at the shingles. If your roof cleaning solution has not been tested previously, make sure you test it on some spare shingles before applying it to your roof.

Do not scrape the moss off of the roof. This can rip, crack, and break the asphalt shingles themselves.

Best practice is to treat for moss early in summer, then  gently use a leaf blower to remove loose and dead moss after treatment. Preferable in the late summer when is has dried out.

If any water is used to remove the moss, do not spray the water at an upward angle. If you do, this can cause water to go under the shingles and leak into the house or rot the wood decking of the roof.

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JJ Greive

JJ & Suzanne are both licensed, highly skilled inspectors and educators. We are the authors of our class curriculum, and truly enjoy sharing this with our students