which roof plane drains the highest volume of water?

my5sons

I have 2 questions, and this may seem brutally obvious to all of you, but
1. Which one of these roof planes drains the highest volume of water? Looking at the drawing below, original blue roof is 4/12 pitch and is about 55 feet long, the shingled portion (my porch add on) is 2.25/12 and 40x20 ft the Pink roof is 4/12 and 22x20 ft. My guess is the 4/12 garage will move the highest volume of water and I should shingle the 2.25/12 pitch first, and cut the garage shingles 2" from valley center. Am I correct?

2. If I do a closed cut valley, should I start shingling from the rake into the valley, or shingle OUT of the valley? How do I determine that I won't end up with 1/4 of a shingle at either end?

Thanks in advance for any and all help!

tinner666

I prefer to shingle out of the valley. Using dimensional shingles, you don't have to worry too much about the ends, but it can bite you. Here and there near the edge, you might have to piece in some 12" - 28" pcs.
A 1/4 shingle isnt too small to use. I've used 6" when necessary.
Not sure which plane as drawn will have the most water, It looks like the original roof will to me. I notice the ridge is above the valley top there. Run it under never less than 14", and cut the other side 2" from center. I like to taper the cut from 2" at top to 3" on bottom.

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Frank

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BamBamm5144

If you do a closed valley, follow what tinner says but instead of having to worry about that, why dont you do an open metal valley?

Are you using dimensional or 3-tab shingles?

tinner666

Open valleys are nice too. One creavat: You have to cut the shingles ends off properly. BTE, you have to do that either way! I forgot to mention it earlier.

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Frank

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tinner666

These pics show the correct way. The picture I posted just before, is what happens when the tops aren't clipped.

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Frank

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my5sons

I am using Timberline 30 Laminated Shingles. I think they call them architectural. I thought about a metal valley, but not sure where I order one from. I'll be ready to shingle this weekend again. There was a lot of stuff I would have done differently if I had to do it all over again. In the meantime, it is what it is...