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I do a lot of open valleys here with 'w' flashing, they seem to shed the conifer needles better. I was cutting into a roof to tie in an addition and noticed something I hadn't seen before on the existing valleys elsewhere on the roof. The previous roofer had run a row of shingles all the way up the valley 3" from the 'w' before putting even the starters on. Then he'd shingled like anyone would with the exception that he hadn't cut the valley angle on the shingles adjacent to the valley, simply started with a square end that met the valley at the 3" mark. Relying on the first row up the valley to dump the water. He'd also started from that end so on this pitch he had about a 6" offset each course. This sure saves some cutting, what do you guys think? Rich.
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I think it is like those that do not want to take the time to do it right and will lay a straight shingle up the cut side of the valley and run the shingles into it, no cut. WHy not do it right? To pinch pennies? Who wins in the end? The customer? Lets not go remedial with peoples' lives, ok?
I agree with Aaron B. No shingle mfr that I know of recommends this. Very straight and fast, but ends up with only one layer of shingle material at the small triangles in the valley. Makes "uphill" ridges with architectural shingles.
Jim
Tamko recommends the vertical shingle method of installing "closed cut valleys".
on the shingle wrapper.
I do not like the look of the pre-form valley with the shingle run up the valley with the shingles running across the roof gapped back and not cut to the valley line. Nothing looks better than the California style, or closed method. Less money for valley metal, no eye balling valley metal, 50% less valleys to cut and less scraps to toss off the roof.
We call this technique (which is NOT allowed by any shingle mfr) "cheater valleys". A no-no around here. It leaves only one layer of shingle at a roof's critical area!
Jim
I'm pretty sure you just spoke of the owens corning spec.

I've tried that on a couple houses to see if I liked it. Honestly I am indifferent, however would never do it on a 3-tab. it only works with architecturals.
Jmorgan look on Tamkos shingles its how they illlustrate to do it.
Because this guy in the link does it this way....means its ok?
I figure if the manufactuer is comfortable giving a warranty with the valley done this way they must be confident that it will hold up.
Not at all ! Just showing there is more than one way to skin a cat. Go with what your comfortable with or what the manufactuer suggests. If you go with there suggestions and the roof fails...... hopefully the liabilty will be on them.
AaronB. said:
Because this guy in the link does it this way....means its ok?
Have yet to lay laminate shingles for a manufacturer that calls for all the shingles to be offset 4-6 inches up the roof. Most manufacturers call for running four shingles at a 6 inch offset then splitting the fifth shingle in half and starting over. Only other way I seen on a shingle wrapper called for a 10 inch offset from top to bottom.

The guy on roofing911 sure uses a lot of chalk lines!
Am I the only one who has seen the Tamko spec on doing vertical shingles in the valley? I do live in California. Maybe it's different out here.
we do our valleys like that all the time in b.c,never had a problem and its a great looking valley
This is the only way we do valleys. It is the only way to seal the valley and have no voids in arch. shingles. This way you don't rely on your tarpaper and iceshield to keep the water out. This is especially on low pitches. If you haven't seen a 4/12 pitch with arch. shingles cut with a knife, leak, you haven't been roofing long enough.

Again, I can take pictures to prove my findings. There is voids for water to pass if you cut down a valley on arch. shingles.
One pic from last winter on how to do valleys correctly.

Certainteed does honor this method.

Leaving a space is not a bad idea, but we run them tight and never had a problem.

Attachments

Look at the bags of the shingles you use. Landmark and Timberline only call for a minimum of 4" offset.
Have yet to lay laminate shingles for a manufacturer that calls for all the shingles to be offset 4-6 inches up the roof. Most manufacturers call for running four shingles at a 6 inch offset then splitting the fifth shingle in half and starting over. Only other way I seen on a shingle wrapper called for a 10 inch offset from top to bottom.
If you look in the MSA manual the recommend the following rack

full shingle
33 1/8"
27 1/2"
remaining piece from 27 1/2"
remaining piece from 33 1/8"

We have a large paper cutter to pre cut all racks on the ground.
Not every roof is rake to rake shingling. This is why the manufacturers state a minimum of 4" offset.
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