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Roof valleys lined with 3-tab shingles


randynavarro
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Shingles with should be aligned in such direction that rainwater drains parallel to the sides of the shingle. There are some exceptions but this isn't one of them. Couldn't find a document. It's a cardinal rule in roofing.

Marc

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They should have flipped those around so that the joint comes every 3ft., nipped off the corners and adhered that cover to the valley on both sides with a 20inch wide band of mastic.

Mike, I never heard of anything like that. 3 tabs aren't a replacement for an underlayment of 60# felt or 3' roll roofing.

Marc

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Anyone have a problem with this?

I couldn't find anything specific in install manuals stating this isn't allowed.

I first started seeing this about 10 years ago on closed cut valleys using laminated shingles -- not three tabs. It works fine in that application. Mike Guertin wrote an article about the method in Fine Homebuilding back in December of '02. He called it a Long Island Valley. Certainteed recognizes that method and called it an "Alternate Closed Cut Valley."

I don't much care for the use of 3-tabs and I'm not aware of anyone who endorses using it with metal valley flashing. However, I've seen it done several times and it seems to work fine.

- Jim Katen, Oregon

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It seems to me that the horizontal gaps between the tabs would encourage water under those shingles and also direct water under the neighboring laminated shingles. I suspect it is only working, so far, because of the felt.

"I couldn't find anything specific in install manuals stating this isn't allowed."

As with most codes and manuals, they just can't anticipate all things stupid. They tend to stick with what IS allowed. I would call it because it screams wrong to me...and leave it up to the roofer to prove me wrong.

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Randy wrote: Pabco has a spec. sheet, that although they don't "prefer" it, they consider it acceptable.

Their detail shows laminated shingles and not 3-tab shingles, however

Richard wrote: It seems to me that the horizontal gaps between the tabs would encourage water under those shingles and also direct water under the neighboring laminated shingles. I suspect it is only working, so far, because of the felt.

Marc wrote: Mike, I never heard of anything like that. 3 tabs aren't a replacement for an underlayment of 60# felt or 3' roll roofing.

Which is why you flip the shingle around backward and place the un-nothed side along the valley. In that configuration it's exactly the same as the laminated shingle except smoother and thinner and allows the shingles abutting the valley to lie flatter and gives it a cleaner look.

My father taught me the technique somewhere around 1968 or 1969. I don't even think they had laminated architectural-grade shingles back then. Anyway, Certainteed calls it an "alternate closed cut valley" technique in their master shingle applicator manual. They don't show it used with a metal valley but it works just as well with a metal valley as it does with a closed cut valley.

No, it's not a substitute for underlayment; I never suggested that one omit the underlayment or anything else.

ONE TEAM - ONE FIGHT!!!

Mike

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