I’m getting ready to start putting the shingles (50 year asphalt) on the roof of a small cabin in coastal Calif. We get a lot of rain, but no snow. The roof is roughly 12/12 and it has a couple of small dormers. The big question for you guys that do a lot of roofing is: should I use open valleys with W flashing, or closed valleys, and why. Is one better than the other, last longer, or ???
Thanks for the advice
Loach
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Replies
if you're talking 3-tab, or the thicker 'timberline' types of the same size/dimension, only thicker and/or multi-layered (as opposed to any kind of 'T-Lock" type), i'd definitely recommend closed valleys. however, the final word(s) on the subject lie with a)the mfr and their installation and warranty specs, and b) your friendly local bldg inspector.
12/12, you say? oooh, you poor ba$tard... (i used to lay shingles for a living)
m
I prefer open valleys to let the water run out on metal.
With closed valleys the shingle life expectancy is shortened by water wearing away the valley shingles faster than those in the field.
I would insist that my own roof be done with copper valley (w or otherwise). They can tell you anything they want about those shingles ... I've seen the old copper. It holds up well. Coincidentally, just had this discussion today with a roofer/framer that was working for me for the last few weeks. He agrees.
I second Don's advice...not only will you waste a lot of expensive roofing with closed valleys, but those thick shingles are hard to get to flex in the valley without cracking. Use copper W flashing--it will complement the expensive shingles and you won't ever have to worry about valley metal corrosion.Jason Pharez Construction
Framing & Exterior Remodeling
Terne....that's what the old one's often were....copper's nice if you can afford it.....
Loach, what do you prefer?
I wouldn't have an open valley. I don't like the look.
blue
You got a funny looking name there, Blueeyeddevil..........
Joe H
Well Blue eye,
I kind of prefer the look of the closed valley. The open valley looks like each plane of the roof was cut in separate, and the eye is drawn to the separation. This roof is on a small cabin in the back of beyond, and the only valleys will be on 3 small dormers with about 6 feet of valley per side, so I'm not sure the "water will wear out the valley shingles" argument will work. My big reason for asking was to try to find out the reasons that people prefer one over the other. I've seen them done both ways, and I'm sure there are good reasons for each way. If one is overwhelming better, I'd like to know before I start the job so I can plan accordingly. 12-12 Sheesh!
Loach
Since your dormer valleys are small, it sounds like you could easily go either way.
Up here in the Northwest, heavier 50 year architectural shingles are usually installed with metal valley. Sometimes the heavier 50 year can buckle or crack when shaped into a closed valley especially if it's cold. Also you may notice a slight hump one side of the valley where the shingles run underneath the cut side (I would steer away from a full woven valley).
To meet new code up here, we need to use either metal valley or line a closed valley with ice & water type underlayment (or cap sheet). The ice & water may seem like overkill where you live without snow, but it could be cheap insurance for 36' of valley.
If you have a lot of overhanging trees, the metal valley might shed debris better.
A thick laminated long-life shingle like that will not not flex easy into the valley, so there will be fractured shingles. i'm an open valley man, but do it any of six ways, according to what is best for each house.it is not the length of the valley that determines water wear, but the amt of water running through the valey. That comes from climate, and the height of roof area above the valey on each side.
I'll bet my eyeteeth (and I'm a meat eater) that a woven or lapped valley will be worn through long before your fifty years is up
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yeah, i got to thinking about it some more and you're probably better off going with open valleys. the combination of thick, stiff shingles and the tightly angled valleys produced by intersecting steep faces is not gonna work well. a lower pitch roof might be okay closed, but not this one. once again, go with mfr regulations and local code for the last word.
have fun!
m
Thanks for the input. It sounds like the standard for a roof this steep is open valleys. I'll be starting as soon as the dormers are dried in. It's a small roof, so this should be fairly quick. I kmew I could count on the forum to have opinions!
Loach
If you don't want to see exposed metal, you do not have to have a W valley open. It can be cut closed. You cut the shingle at the base of the center ridge in the valley metal. The ridge keeps water diversion straight, keeps the cut line straight, baffles wind, and all you see is a nice neat straight line where the opposing shingles meet.
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