# Mildew/algea on roof



## uts (Jul 8, 2019)

Anybody has any recommendation for cleaning out some light mildew/algae/moss on the shingles.

I tried using wet and forget from costco and did three applications 3 months apart but havent seen much of an improvenent. That said I did do it in the fall to very early spring so maybe the temperature was wrong.

This is what the worst part looks like. This faces the north.



If anybody has any recs that would be great!


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## bosox_5 (Jun 20, 2018)

Zinc strip on the ridge vent

https://www.google.com/amp/s/www.thisoldhouse.com/platform/amp/roofing/21015851/preventing-roof-moss-with-zinc-strips


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## daniel3507 (Jul 31, 2018)

Zinc strip was going to be my recommendation as well. If you can do it safely I would get up there with a bleach solution and brush to kill and remove what you can. The zinc would take care of the rest and prevent more from growing

https://youtu.be/f_jbaGCR6oo


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## kstall (May 10, 2019)

That needs bleach. Using a brush on it could damage the shingles so I wouldn't do that, but that's just me. If you are using store bought bleach then use it full strength. Most store bought is around 6.25% SH. If you have a pool store close by get some liquid pool shock. That should be 10% SH. If you get 10% cut it 50/50 with water. If you can safely get on the roof, put your bleach in a pump sprayer and soak the crap out of it. I mean like drench it. Climb down and leave it on. The next time it rains it will clean it off. It may take a couple of rains. But leave it on and let the SH do its job. If you have a pressure washer you can use the chemical injector and spray it from the ground. But DO NOT use high pressure tips! Use the soap tip. Dont rinse it, just leave it. The moss and algae will turn white after spraying and mother nature will wash it off.


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## M32075 (May 9, 2019)

I used spray and forget worked good not great. Took some time to work it's not instant.


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