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Once read or heard that placing strips of zinc or copper (?) at the ridge would supposedly prevent green stuff from growing after a rainstorm.
Supposedly as rain water washes down, the trace amount of metal leached would kill the green stuff that typically grows on the north side of a roof.
Does anyone have first hand experience? or this an old wives’ tale ?
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The concept can work, though there could be a bit of streaking involved. Check a roof just below the sanitary vent, and you'll usually note that area is clear of mold. By the way, most roof growth is an algae that is windborne. Killing it with bleach won't prevent it from reappearing unless all homes around yours are also free of it.
*Tom: There are also powdered zinc preparations, designed for lawns, that might have an effect in knocking down the moss on the roof with less trouble than installing zinc strips. Available in any garden center in the Seattle area where it seems to be common knowledge that zinc kills moss. -David
*A year ago, I installed zinc strips at the ridge lines of my composition roof, and all moss has disappeared. My house was 5 years old at the time, and I noticed moss buildup of about 1/4" in several places.By the way, I live in Seattle (you know, the place that rains all the time) and some neighbors have up to 3 inches of moss on their roof! Average moss buildup in this region seems to be about a half-inch.
*Yes, it (Zinc strips)really does work. As mentioned above, there may be some "staining" of the cedar shakes, but it should be fairly uniform. Installations is really not that difficult, and after it's on, there is nothing else to do. Rather than treating the roof with powder or a zinc solution periodically, the strip does it for you every time it rains. It actually prevents the problem from developing, rather than fixing it every time it recurrs.
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The zinc strips are the way to go. The zinc solutions kill the "moss", but just like weed killers, the dead plant remains and must be mechanically removed. Prevention is best. I have a composition roof that I'm unwilling to penatrate with a nail to hold the zinc strips so I'm still using solution and lots of roof sweeping, but a shake will hold a nail. If anyone knows of a good way to attach zinc to composition roofs, please post.
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Tomm,
By "composition roof," do you mean asphalt shingles? If so, I believe they take nails. You should be able to lift a ridge shingle, insert and nail the zinc strip (Shingle Shield) under it, and lower the shingle.
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Does anyone have any figures on the relative cost of cedar shakes vs asphalt roofing? I have heard that it is not wise to use cedar if you have a fireplace or wood stove. I figure that a roof fire would be as likely as a lightning strike but who knows.
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John,
I put a cedar roof on my house 6 years ago. 2 lightning strikes so far, but no roof fires. I've got a stove and a fireplace. Both of those flues are fitted with stainless steel spark arresters at the tops.
Jon
*Marginally on the subject. When I was a kid I had to take care of a pool in our neighborhood. I earn $5.00 a week.(mid seventies) Anyway, this old fart neighbor told me that "Bluestone" (copper sulfate) would kill all the algea that grew in the pool. As a guy always looking for a better way I went for it. It sure beat tons of chlorine and tons of scrubbing. My dad brought home the magic stuff and with the old fart's supervision and blessing we added some (a small amount) to the pool. Well the copper works, it killed the algea, it also turned the pools light blue paint brownish. The pool looked disgusting, like I never had cleaned it once the entire summer. The rest of the neighbors were not amused and the old fart who was the Association President never did come to my rescue. I worked harder than ever and used more chlorine than ever and it never really looked inviting the rest of the summer.But copper and I'm sure zinc work.
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I put a new cedar roof on my house three years ago and once I'd finished, I filled a garden sprayer with Cuprinol (contains copper, a fungicide) and gave the whole roof a good spraying. The Cuprinol soaked into the bare wood shingles and I haven't seen moss or anything growing on the roof.
*Yes, zinc seems to work all around us (Seattle); roofs next to ours are free from moss. I put some zinc strip on a terrible roof and it worked. The only problem was the old moss died and then was washed into the gutters...and that was a mess to keep the flow of the water going.Hope that helps.
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Once read or heard that placing strips of zinc or copper (?) at the ridge would supposedly prevent green stuff from growing after a rainstorm.
Supposedly as rain water washes down, the trace amount of metal leached would kill the green stuff that typically grows on the north side of a roof.
Does anyone have first hand experience? or this an old wives' tale ?
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I know of a couple applications where a hevey bare copper ground wire was installedon eithr side of the ridge nad it worked. If memeory serves, a bead of roof cement was laid and the copper pressed in with the top exposed.