Moss on slate roof

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Hi,
On the north side of my house I have moss on the slate roof. I'm concerned that it's pushing the slates apart. My roof is 90 years old.
How do I combat this problem?
Thanks,
Aaron
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If it doesn't leak ignore it. Otherwise, contact a slater (not a roofer) and get the right kind of help to rermedy the problem.
Joe
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A friend of mine owned a business in Vero Beach FL for years. He would treat roofs for mold and moss and mildew. The treatment consisted of a regular spraying with a diluted bleach solution. No scrubbing. The normal rainfall would wash everything off. I would think that once it was treated a few times, the moss would lose its grip and be able to be washed off. Wash from the top down, and don't blow the water into the joint overlap. And be careful when walking on that old of stuff. I'd try just a pump up sprayer, and a good strong sprayer, and try it from a ladder or scaffolding before actually going up on the roof. The moss could be slick, particularly after you hit it with bleach. Use proper safety gear, and be sure someone is videoing for America's Funniest Home Videos.
Once you get it under control, I'd still spray it every couple of months to keep it from getting started again.
Steve
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Aaron Fude wrote:

Wash the roof regularly (quarterly is probably good) with a bleach solution.
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Pete C. wrote:

He said Moss not Mold. Will bleach kill moss? And how does one wash a roof with bleach?
Lou
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Yes With a scrub brush would probably be best.
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LouB wrote:

Bleach kills moss just fine.
I've used a pressure washer with the chemical feed from a bucket of bleach solution on a stone patio in an area that grows moss and algae. I've also used this on an asphalt shingle roof in the same area with good results. Pressure washing with bleach solution kept the moss and algae away a lot longer then pressure washing with plain water. I suspect that walking on a slate roof with a pressure washer gun might be a bit dangerous, so you may need to do this strictly from a ladder.
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Pete C. wrote:

Unless you have a tall bucket truck, easier said than done. Almost all slate-roof houses I have seen are 2-story with a steep pitch, and the last thing you want to do is to walk on old slate, unless you are an expert. There is a reason that even historical restoration people are starting to embrace the faux slate made out of old tires and stuff. In cold wet climates, real slate beats wood shakes and thatch, but it is still an expensive PITA.
-- aem sends...
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aemeijers wrote:

Yes, I wouldn't recommend walking on wet mossy slate, working from a ladder or scaffolding would be better. Rental aerial lifts are a lot more readily available these days and I'd recommend that for the initial washing to get the moss off. Once the moss is off, a regular wash from a ladder with the bleach solution should keep it from coming back to the point of needing extensive cleaning again.
I recently rented a nice self propelled 45' reach aerial lift that is light enough to be trailerable with a normal truck (requires outriggers to be lowered before you go up, but all hydraulic controlled from the basket). One nice feature with this boom is that it had built in hoses for air tools and for pressure washers, so you just connected to the quick connects at the bas and in the basket and didn't have dangling hoses in the way.
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september.org:

I don't think that slate by itself would support moss growth. While it is possible that the slate is deteriorating to the extent that it is generating a growth medium, it seems more likely that debris is collecting on the roof and shade is protecting the moss from drying out. SO the question is whether there are increasingly large trees leaning over the roof where there were none before.
--
Best regards
Han
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Han wrote:

There are mosses, algae, lichen, etc. that will happily grow on barren rock if it gets adequate humidity and diffuse sunlight.
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Aaron Fude wrote:

Get moss killer from HomeDepot. It concists of ground zinc, copper and other acidic metals. Sprinkle it all over the moss. Moss don't like acidic environment. You may have leaf/mulch build up on your roof making soil for moss to grow. Clean the roof.
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A zinc strip at the top of roof is common where I live, Laundry bleach will kill it now but moss grows in debris , is roof covered by a tree and not steep pitch so it collects dirt. Mold or green coloring is common and no harm but moss to me means roof doesnt clean itself by rain, by moss you mean it is maybe 1/2" thick and it pulls up intact? My slate roof has green mold, but no buildup in thickness. Moss would be a problem. The only true moss I have or have seen grows on the ground. Roundup will kill it but take longer and cost more than bleach.
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wrote:

Moss does not like pulverized lime, but that will color your roof white. The are moss killers you can apply.
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Phisherman wrote:

I like the inexpensive bleach solution, but won't my roof and back yard smell like bleach?
I don't know if it's moss, but it's a moss like substance that grows on the spaces between the slates on the north side.
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Aaron Fude wrote:

For about a day. Bleach (Sodium hypochlorite) breaks down very quickly into, er, very bad wine and small pebbles.

Perhaps you should contact your county agriculture agent to discover exactly what condition exists. He can also probably recommend a solution. Even a solution of Sodium hypochlorite.
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Slates have two big nails holding them. 5ft of snow or a person wont budge them. Moss in between shouldnt cause harm, they lift a bit, look underneath to see if it grows under slates, minimal green growth wont hurt anything , you made it sound like the roof is covered with moss which to me means debris and dirt, then the roof wont breath and wood will rot, a photo is always a good idea. Bleach smells only a few days, a garden sprayer pumped up with a straight spray might reach 8-10 ft
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Aaron Fude wrote:

other acidic metals. Sprinkle it all over the moss. Moss don't like acidic environment. You may have leaf/mulch build up on your roof making soil for moss to grow. Clean the roof.
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wrote:

I used to be able to buy Copper Sulfate for the garden, I cant now because its poisonous. Sprinkling copper, Zinc, and" metals" might require serious caution, I would not want wind blowing in my direction, and on a roof you can get crazy winds since they deflect of the house. Maybe in a liqued solution, but I used Copper Sulfate to Kill Trees, a dust mask is not good enough protection with CS.
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