Roof Moss Treatments - 5 Ways to Quickly Kill Moss on your Roof

Roofs are meant to shed water and dry out when sun and wind. When roofs have moss that obstructs the water from flowing straight down the roof, then roofs can and do leak. Many insurance companies send out inspectors who take pictures of roofs and look for moss on roofs. Here are some ways that you can treat moss on roofs to kill it and to keep it from regrowing.

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After you have removed the leaves and needles from your roof, you many notice lines or clumps of moss growing on your roof. Dealing with moss is simple. Moss cannot grow in alkali conditions. Again, alkaline conditions on your roof will kill moss and keep it from growing. While acid rain will encourage moss growth, putting an alkali chemical on your roof will kill moss. There is no way around it. Moss likes acid conditions but will die in alkali roof pH.

There are several ways to kill moss. There are several ways to prevent moss from coming back. Remember, moss cannot grow on an alkali roof (opposite of acidic roof).


Use all information on this website at your own risk. This is for educational purposes only. Your reading this is consent that you agree to indemnify me.

Here are ways to kill moss. And no, I currently have no financial gain from any of my recommendations. They are based on 11 years of previously being in the moss treatment and removal business in Portland, OR.

Lily Miller Moss Out for Roofs Heavy Duty Cleaner will kill moss. This product is sold as a "moss stain remover", but the fact is, it contains lye, sodium hydroxide and as the word "hydroxide" implies, it is very alkali. Remember? Moss cannot grow in alkali conditions? Well, lye or sodium hydroxide (mixed per instructions) will create an alkali roof VERY quickly and kill moss. It will also rupture algae cells which will explode releasing all their pigments. Spraying a roof at the prescribed mix ratio onto a algae covered roof will (make it slick) cause the cells walls to explode, releasing a grean, black and brown wash that looks like sewage. The beatiful thing about lye is that with the right mixing ratios, you can spray this on your roof and let the rains wash the dirt off! Yes!. Let me repeat, you can spray this on with the proper mixing ratio and let the rains wash off the dirt. With each rain, your roof gets cleaner. It may take more than one application, depending on how dirty your roof is. This is a great product in my opinion for ease-of-use and effectiveness at killing both moss and algae and cleaning your roof. It is not a licensed pesticide, so they don't advertise it as such, but it does work as a moss killer. It also helps prevent moss until all the lye has washed off your roof.

Lily Miller Moss Out for Roofs, Moss Kiler for Roofs. Contains 99.9% zinc sulphate. Great purity for its price. 6 lbs costs about $15. Is mixed with water and sprayed on moss. Zinc in abundance dries out the moss and so the moss dies. Zinc sulphate has acid pH, but it works through the zinc. Works great when sprayed under the roof shingles where it cannot weather off. Moss likes to grow its rhizomes between the shingles, and if zinc is there, it will die. As with all chemicals, read all the directions on the label.

Bleach water of about 1%?? (I forget exact percentage) overall concentration will kill moss. I think straight out of a bleach bottle it is 5%. If you dilute this will 4 bottles same size of water, it will make 1% concentration. Bleach or sodium hypochlorite will cause chlorosis (destroy the chlorophyll) in moss. This turns the moss yellow (ugly) and will kill the moss. Bleach at this concentration is powerful and chlorine gase fumes can overwhelm a person on a roof. They usee the very effective chlorine gas to kill people in World War 1. Imagine falling off a roof after being overwhelmed by chlorine fumes from bleach spread all over the roof. Bad idea! Bleach will kill moss. Too much bleach concentration will damage the roof shingles and will void warranties on roofs. I believe that 1% concentration of bleach or less will not void roof warranties. Check your warranty and get it in writing from your roofing manufacturer that supports the warranty. Roofing companies would never put it in writing for me. Use at your own risk. Some people use laundry detergent to kill moss, but in most cases, it is the bleach in the laundry detergent that kills the moss anyway.

Some people advertise roof cleaning, spray on a 5% solution, wait a little time and then powerwash it off. I can think of better ways to make a living and better ways to clean a roof.

Laundry Detergent will kill moss. I don't recommend it. Here's why. The laundry detergent will remove oils from your asphalt roof, dry it out, and cause immense damage to roof when granules drop off and the UV rays from the sun crystalize the tar in your shingles, causing microfractures and eventual leaking. Many claim laundry detergent will kill moss, and it does, but it will ruin your shingles. The purpose of treating moss on roofs is to protect your roof. Don't destry your roof with laundry detergent.

Ammoniated soap of fatty acids is and ingredient found in some license moss killers. I don't recommend it. I have seen it marginally effective. Never apply this and then spray zinc sulphate on your roof. They will chemically combine and make your roof white. Also, maybe toxic byproducts of zinc sulphate and amonia? Also, this stuff puts fat on your roof. Ugh! I don't recommend products containing ammoniated soap of fatty acids. Sorry.