California cut seal?

We had a new roof installed in November. GAF Timberline HD with all the GAF components required to qualify for the GAF System Plus Lifetime non-pro rated warranty. The valleys were finished with a method they called a “california cut”. These cuts that run straight up each valley don’t appear to be sealing down at all. Water and debris is infiltrating under these areas. Is this join supposed to seal down solidly? If not, what’s to stop the first hurricane wind from lifting it and peeling the roof off?

I uploaded another picture of the valley with the area not lifted by a boot but I’m only allowed to post one picture.

Looks wrong to me. Do you have mastic under the “starter” shingle that runs up the valley?

Nails have to be 6" out of the valley, in a hurricane zone I would want a thick bead of cement to glue those down.
Make sure it’s a couple inches back

1 Like

The starter shingle going up the valley is probably only nailed. The skinny tape is under that starter. I think maybe that’s a fail because (according to the material list) that material should be GAF Asphalt Starter peel and stick. If so, it sure didn’t stick.

As you can see from the other tapes under shingles, nothing else in the area has sealed well at all. Everything is similarly loose. All of the tapes are under a different layer of shingles. We’ve had plenty of hot days since the roof was done but also a lot of wind and rqain. Most of the roof has sealed but these valleys and a lot of the TimberTex caps have not sealed well at all. The poorly sealed valley areas I’ve looked at have water and small bits of debris beneath.

I can’t find any mastic or cement or anything similar anywhere. I think I better call the contractor back out to have a look at all this.

It’s called a closed cut valley and it’s fine quit messing with it.


As axiom said it is a closed cut valley and will be fine as long as you do not keep lifting up the shingles.

I cannot tell from you pictures, but make sure the top of the shingle has an angled cut downward where the shingle intersects the valley to prevent water from traveling horizontally across the top of the shingle.

Other than checking that everything else looks good.


Thank you all for the information. I’ll have the contractor determine why so many of the shingles aren’t properly sealing and he’ll take the appropriate action.

Im thinking he might even need repairs in the future where he lifted the shingles up with his boot
In the valley because that disturbed the fasteners.
Probably not, but he is pushing it.

The roofing cement installed in the valley is not for water proofing, it is for wind up lift in hurricane prone areas.
And No we dont cement all the way to the cut or even close.
If we did, the roofing cement would be squirting out everywhere making a horrible mess.
We cement under where we would be installing the roofing nails in the shingles.