Replace or Reuse old valley flashing On Home

I will be ripping the shingles off my home and was thinking of just covering the previous valley flashing with Ice And Water Shield. Would this work if I filled the current nail holes with roofing tar?

My second option was to tear out the old flashing and just put in a Ice And Water Shield than weave the shingles over the Ice And Water Shield in the valley.

In your experience what is the best way of doing this?

Thanks I am new to roofing.

-Roof Pitch 6/12, Architectural Shingles

Best practice is tear everything out. Apply ice and water directly to wood deck. The rest depends on your local codes. Here in pa only ice and water is required, but we always use a layor of 90# on top of the I&w for extra support and an extra layor of protection before installing the shingles. Depending where you are the code may require more or less.

Do not weave the shingles in the valley unless they are designed for that. Look up a California cut valley. Personally I either do calafornia cut for closed valleys in architectural shingles or open metal valleys for architectural or any other types of shingle.


The IRC code is a valley lining of 90# felt, valley metal or IWS period. I’ve never seen more required. I certainly would not reuse valley metal.

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For 6/12 i use two layers of felt.
(One run folded in half)
And then 26 gauge steel rolled valley.
Closed valley.

Are open metal valleys common where you live?
Almost everyone here uses them, and for roof reason.they work very well in snowy areas.

I’m learning a lot from this thread. Will be taking note of these as well.

Patchap, I live in Northern Utah and most older homes seem to have closed valleys. Open valleys on newer homes here seem more common.

Currently I’m conflicted if I can just use Ice and Water Shield in the valley and eves then run synthetic underlayment about 6" into the valley and use a closed valley (I started running the synthetic underlayment over the Ice and Water Shield and across the valley onto the other side which was a real pain) so I’m looking at other options.

This is what I was thinking of doing…


Would it be okay to run a piece of synthetic over the I+W shield in the valley (top to bottom) instead of 90#?

What you have now, if that’s your picture, is fine. You can install a closed valley right over it.
If you install a layer or synthetic over the ice and water, the shingles won’t stick, which will be a big favour to the next guy.
It’s not necessary, however.

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Thanks. That picture isn’t mine but what I will be shooting for hopefully. As for a California cut valley would it be to complex for a beginner roofer? I’ve only done three tab closed valley so far.

California valleys are simple and work great. The important part is the overlap, which you’ve done before so that shouldn’t be a problem.
When your installing the Cali part, watch your offsets. Depending on the pitch you need to cut the shingles for every course, or they wind up being to close.
4-6/12 you should be okay. Steeper and they need to shrink as they go up the valley.

You have been very helpful thanks. One last question how do you determine which slope to start on first? Here is a picture of the roof.

(This picture is missing the I+W shield on the bottom right and the underlayment)

California valleys are a shortcut and the least desirable way to do a valley with shingles.

Carry on.

Would a Closed-cut valley or a Long Island valley cut work over a California valley? I would like to do the best cut for Tamko Heritage shingles. I will be using only Ice and Water Shield in the valley and eaves like the picture below. Thanks


I use either a closed cut valley or open metal.

IMO the open metal valleys are a bit better but harder to install correctly.

The California valley is all about speed at the expense of everything else that matters, and they encourage incorrect staggers.

Thanks for your help. I think I will go with a Closed-cut valley. I’m debating on whether or not to use galvanized steel valley roll flashing or aluminium valley roll flashing over the Ice and Water Shield or just leave the Ice and Water Shield by it’s self (assuming I’m using a Closed-cut valley).