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Open versus closed valley


Jeff Beck
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Is there an advantage to having a closed valley versus an open valley, or vice verse?

I've seen open copper valleys with slate and galvanized open flashing with just about everything else but never have really known why one style was preferred over the other.

Jeff Beck

Foresight Inspection Service LLC

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By "closed" I'll assume you mean a woven valley or a closed cut valley?

I would think closed valleys are simply cheaper. No metal is required and not as many shingles need to be cut unlike a metal valley where each shingle needs cutting to line it.

Other than that, if done correctly I would say that either closed or open peform equally as well if the right materials are used.

Some purists might come along though, and completely disagree with that statement.

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I almost always weave or install a closed cut valley over aluminum. I know it's overkill but when I install the aluminum I staple one side then use a roll of felt to shape the valley as I staple the other side (staple=whacker tacker). The gentle radius lets the shingles make the transition from plane to plane better and keeps the laminations from separating.

Metal valleys shed snow and debris better than the shingled over varieties.

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I almost always weave or install a closed cut valley over aluminum. I know it's overkill but when I install the aluminum I staple one side then use a roll of felt to shape the valley as I staple the other side (staple=whacker tacker). The gentle radius lets the shingles make the transition from plane to plane better and keeps the laminations from separating.

Hey, I used to use that same technique. (Well, except I wasn't anal enough to use a roll of felt, I just set the coil stock with a nice fair curve to it and tacked it in place.) When I build my present house in '91, I showed that technique to the roofer -- he'd never seen it before. I know he thought I was nuts, but he was nice enough to use the technique throughout.

Times change though. When I built an addition a few years ago, the roofer asked, "You want me to do anything special with the valleys?" I just said, "Do what it says on the package and make sure they don't leak."

I'm getting more & more lazy as I age -- even when all I have to do is tell other people what to do.

- Jim Katen, Oregon

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Closed cut is the easiest and looks just fine imho. Never liked weaves for some reason.

If you're using shake, tile, or stone, nothing looks nicer than open w/ridged metal like Kibbel just described.

WR Grace under everything makes any valley work longer than anyone will care.

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As stated above, either can work fine given due attention to the details. Personally I think open valley's belong on certain style homes and are more appropriate for a steeper pitch using composite shingles, as when the pitch increases the angle between the two planes that the shingle must be bent into becomes more acute. This goes double today with the laminated shingles. On the other side of that coin, use an open valley on a lower pitch roof and you can have more danger of falling tree branches poking holes right through the sheet metal, which I find often.

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A swept valley is the prettiest.

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The third course up on the left side is uneven. I think he should redo it.

- Jim Katen, Oregon

To my eye, it looks like more then just the third course. The angle of the picture may be skewing things a lot from what they really are but it looks like the arcs, angles & exposure are running off.

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I would starve to death doing that kind of work. I find it impossible to keep my furnituremaker's blood from running the show. Any of my friends seeing me up on that roof would instantly say, "check his tool belt, bet ya he's got a dial caliper in there somewhere" It's not my fault really, I have this geometrical obsession that puts me into the deranged category of anal where that stuff is involved.

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Never had the pleasure of seeing a swept valley. It's all metal and open valleys around here.

What's the roofing style on old English cottages where it looks like there's about 30 layers of shingles that are globbed into a rolling wavelike appearance? My memory for terminology is failing.......

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Never had the pleasure of seeing a swept valley. It's all metal and open valleys around here.

What's the roofing style on old English cottages where it looks like there's about 30 layers of shingles that are globbed into a rolling wavelike appearance? My memory for terminology is failing.......

I know I'm going to be corrected on this, at the very least for the spelling, but I think your talking about Cotswold...

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Monier (in their current ER report) suggests open valleys where you may have alot of organic material falling on the roof. It is a maintenance issue, If you have a closed valley and get debris in it you will have more lateral water movement. Even if you have batten extensions for the slate or tile roofing you will have more of a tendency to overtop the hemmed edge. That is why I typically insist on a valley pan with three ribs. That way debris stays in the cener rib and the two secondary troughs will give the water a clear path.

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Never had the pleasure of seeing a swept valley. It's all metal and open valleys around here.

What's the roofing style on old English cottages where it looks like there's about 30 layers of shingles that are globbed into a rolling wavelike appearance? My memory for terminology is failing.......

When in England some years ago, I heard "wimbly wambly" used to describe something that is wavy. Could be "wombly" though.

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What's the roofing style on old English cottages where it looks like there's about 30 layers of shingles that are globbed into a rolling wavelike appearance?
I don't know of a name of the style other than what I've read in advertisements guides from the first quarter of the last century - "false thatch". The shingles were steam bent to curl over the gable ends and butts cut at angles to create undulating course lines with very little exposure.
I think your talking about Cotswold...

Cotswold Cottage is a style of American home that was built during the first quarter of the last century. I think many seem to be an insult to the actual period homes throughout the Cotswolds in central England.

england-cc.jpg

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