# Killing moss



## KennMacMoragh (Sep 16, 2008)

What's the best roof moss killer?

I tried this stuff from Home Depot 










But I wasn't very impressed with it, I let it sit for two weeks, it says to wait four weeks which I don't have time for. But I came back after two weeks and it looked like it was turning brown, it had been raining a lot too. But it still does not come off very easy with a hose, and I want to try and avoid having to pull out a pressure washer. I have to scrape every shingle to loosen it and then hose it off. Is there something that works better and faster?


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## stombaugh85 (Jul 23, 2012)

Oxy Clean works great


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## KennMacMoragh (Sep 16, 2008)

stombaugh85 said:


> Oxy Clean works great


The laundry detergent?


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## stombaugh85 (Jul 23, 2012)

KennMacMoragh said:


> The laundry detergent?


Yes ,it is like powdered peroxide . 
Melts moss right off.


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## roofermann (Jun 8, 2013)

Please do not pressure wash composition (asphalt) shingles! You will just hasten the aging process, ie loss of granules.:thumbsup:


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## KennMacMoragh (Sep 16, 2008)

stombaugh85 said:


> Yes ,it is like powdered peroxide .
> Melts moss right off.


When you used it, how long did it take to kill the moss? Did it work faster than four weeks like the Moss B Ware? Did you sprinkle it on and let the rain soak it in?


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## stombaugh85 (Jul 23, 2012)

KennMacMoragh said:


> When you used it, how long did it take to kill the moss? Did it work faster than four weeks like the Moss B Ware? Did you sprinkle it on and let the rain soak it in?


Saturate the moss completely , you could also do a 50/50 with bleach and oxyclean but your foliage may die. Moss will be dead within week and roll right off the roof.


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## stombaugh85 (Jul 23, 2012)

roofermann said:


> Please do not pressure wash composition (asphalt) shingles! You will just hasten the aging process, ie loss of granules.:thumbsup:


Nothing wrong with pressure washing . As long as you keep your distance and shoot downhill ,its perfectly fine if you know what your doing.


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## roofermann (Jun 8, 2013)

stombaugh85 said:


> Nothing wrong with pressure washing . As long as you keep your distance and shoot downhill ,its perfectly fine if you know what your doing.


Really? You can guarantee zero granule loss?


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## stombaugh85 (Jul 23, 2012)

roofermann said:


> Really? You can guarantee zero granule loss?


If you dont know what your doing then dont attempt. Its not rocket science. If your blowing off granuals then your too close or pressure too high. 
Use some common sense and you'll be fine.:thumbup:


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## iceman61 (Jul 26, 2007)

Never heard about using Oxy Clean on a roof but it makes sense. Moss likes shade and a pH level of around 5 - 5.5 to thrive. Two ways to change the pH level are use an acid (vinegar or fruit juice) or a base (bleach or dish washing liquid). Since *using an acid on shingles will degrade the shingle composition material to some degree*, I've used a base with good result. Bleach (the kind with the green label used for decks) or Dawn dish washing liquid work good to kill mold. Oxy Clean is a base since it has bleach in it. These are the things I have personally used with good results, all applied with a pump up sprayer. 

Dish Soap Recipe
5-10 ounces of Ultra Dawn Dish Soap
1 Gallon of Water

Chlorine Bleach Moss Killer Recipe
10% – 20% Chlorine Bleach
90% – 80% Water

I usually leave this application on for a month before spraying off with a garden hose. I use a pressure washer a lot but there is no way I would ever use one on a roof. In the simplest form, it's just extra trouble to hook up and have to use as opposed to using a garden hose, not to mention too much pressure no matter how careful you are with it. IMHO it's like dragging out my air compressor, hoses and trim gun to reattach a loose piece of trim when all I really need is a couple of finish nails and a hammer. 

No matter what application you try, you also need to spray off any plants around the eaves of the house or you risk killing your customers' expensive plants. Not good for your reputation no matter how good the roof looks afterwards.

You also need to explain to your customers that you are only treating the problem. It will come back unless the let you prevent the moss from coming back. To prevent moss from coming back, you either have to remove the trees shading the roof or install zinc or copper strips on the roof. Rain washing over the strips will spread the chemical reaction over the roof. Up around the ridge shingles is a good place to install these.

Here in a picture that shows you what zinc will do to moss.


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## KennMacMoragh (Sep 16, 2008)

I am using zinc shields along the ridge. In the process of doing two roofs right now. I don't like to wait an entire month to come back and hose off the roof and collect my check. Also, an insurance company doesn't give you that long if they see moss on the roof, they want it cleaned sooner to ensure coverage. I used liquid MossOut from Home Depot on my last one. The kid at the store says they use it outside and it kills moss in two days. Hopefully it works, if it doesn't kill the moss enough then a garden hose won't get it off. I'd have no choice but to use a pressure washer, but I would use a low psi electric and keep the wand held back.


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## Duke G (Jul 21, 2021)

stombaugh85 said:


> Saturate the moss completely , you could also do a 50/50 with bleach and oxyclean but your foliage may die. Moss will be dead within week and roll right off the roof.


NEVER EVER mix bleach and OxyClean! 
Mixing OxiClean and bleach is EXTREMELY DANGEROUS! OxiClean breaks down into hydrogen peroxide. The reaction of combining hydrogen peroxide and chlorine bleach makes a chemical reaction and poisonous gases.


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## G&Co. (Jul 29, 2020)

KennMacMoragh said:


> What's the best roof moss killer?


Temporary, the cleaning agents recommended in previous posts.
Permanent, zinc or copper strips placed correctly so that rain water washes over them and then washes over the rest of the roof.


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