How to Make a Closed No-Cut Valley
Faster than and just as water-resistant as a closed-cut valley...and it looks almost identical.
Have you tried a no-cut valley (sometimes called a ‘California Valley’ or a ‘Tamko Valley’)? If so, what do you think of it? In my opinion, no-cut valleys are fast to install, water-resistant, and beautiful.
It installs and looks almost the same as a regular-cut valley, where the shingles on the low-volume roof plane are installed first and pass through the center of the valley by at least 12 in. Then, rather than cutting the shingles on the high-volume roof plane, a row of shingles is installed with the exposure edge facing the valley center. The shingles are run from eave to ridge and placed along a chalkline snapped 2 in. out from the valley center. I like to select laminated shingles with a single layer (rather than laminated 2-ply) at both ends so the upper shingle can be laid over the lower shingle by an inch or so without the overlap being noticeable.
I work out of the valley with full shingles placing the lower corner of the shingle at the point where it crosses the valley-facing edge of the starter shingles. Generally, the angle of the valley sets up a shingle joint offset of about 5 in. to 5 – 1/2 in., which is more than the minimum offset required by shingle manufacturers. It won’t usually match the prescribed offset pattern established by shingle manufacturers by their rake starter set measurements. If you want to follow the manufacturer’s offset pattern, you can extrapolate the shingle sizes necessary to achieve it and just square cut the shingles. In that case, it wouldn’t be a truly no-cut valley, but it would be faster than diagonally cutting each shingle.
Tamko is the only shingle manufacturer that shows the no-cut shingle valley process in their installation instructions. I think I first learned of the system reading a bundle of Tamko shingles about 22 years ago and have used it frequently since. I checked with the technical reps from several major shingle manufacturers to see if there were any restrictions against using a no-cut valley process with their shingles, and there weren’t any — other than a caution that if the rake starter pattern of joint offsets wasn’t followed, that there may be some shading differences between shingles that would show
For more about the no-cut valley and to see other valley shingling methods read 4-ways to shingle valleys
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