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guyod 01-26-2008 07:55 AM

Roof valley drip back

With the addition of our very own roofing god and comment about using flashing to stop water from getting into the soffit reminded me a problem i have of my own.

In the summer i put a whole new roof structure on my house, the crack head working for me insured me he knew how to shingle valleys (i had done a couple basic roofs no valleys) so i added a gable end porch roof.. He started a couple coarses of an open valley and i could tell he didn't know what they the hell he was doing. So i picked a shingle bundle wrapper and read it and switched over to an over lapping valley. should of riped up what he did but i didn't thunder storms where on the way.

Now after a heavy rain i notice that the plywood is wet for a couple inches back in the valley. I don't have fascia soffit or gutters on yet.

I'm not sure if its the valley leaking there or if water is dripping back. the other side of the valley which i did does not have the problem.

How is a valley normally made to stop drip back(is there a term for this) since obviously there is a gap in the drip edge there. I was going to put the corner of a square piece of flashing in flush with the drip edge.. is this the best way.

thanks for the help.

glennjanie 01-26-2008 11:03 AM

Hello Justin:
My valleys always begin with a metal flashing the full length X at least 12" wide; that will catch most anything and prevent any drip back too. I'm with you on the woven valleys too. 90# roofing used to be used in valleys and the shingles trimmed back 6" on each side but the 90# has become so rotten and flimsy it no longer works for over 5 years and sometimes fails at 3 years. The shingles woven into the valley with no nails within a foot of the valley on either side allows the valley to outlast the main roof.
I'd like to say a word about the valley sometimes called the 'California Valley'
which has the shingles going through the valley a bout a foot on one side and the shingles on the other side are chalked in the center of the valley and cut off evenly. These are easy to identify by the tons of tar smeared on them through the years as they try to get them to stop leaking.

guyod 01-26-2008 04:29 PM

I did the california valley ..... thats what the shingle bundles recommended. i cant visualize how you weave the valley ill have to look that up.

guyod 01-26-2008 04:31 PM

i just used weather shield in the valley. I heard that is the new accepted thing to use rather than flashing.. is that true

glennjanie 01-27-2008 10:43 AM

Hello Justin:
I'm sorry, I don't know about the weather shield; I suppose I've been out of the market too long.
To weave the valley; lay the shingles in single horizontal rows, let the right shingles overlap the valley by 1' with no nails within 1' of the valley on either side, now let the left shingle row overlap the valley by 1' again without any nails within 1' of the center of the valley, now right run back over, left run back over and so on. Now the center of the valley is flexible and at least 4 layers thick.
With the California valley, the water comes running down the side that is under and wants to continue in that direction which makes it go under the side that is on top, thus you have a leak. When the valley leaks it is extremely difficult to find the leak because it may be several feet above where it runs through, so you end up coating the entire valley and hoping you have hit the spot that is leaking.
Take a drive around town looking at valleys, you will see what I mean.

fireman-175 08-31-2008 11:01 PM

Is there any way to seal a dead valley without hot tar? I would like to fix this leak myself and save a thousand. Any good sealants as an alternative?

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