Roof Valleys

I’ve been doing a lot of roof inspections and one thing I keep encountering on roofs with dormers is that the installers will use a California cut valley but they install the dormer roof shingles OVER the main roof shingles. So the main roof which is larger and located above the dormer is directed UNDER the dormer shingles in the valley, likely being a potential leak issue. I’ve noticed the shingle manufacturers don’t weigh in on this in their instructions but I learned this a long time ago from an experienced roofer when I used to install shingles myself. The proper way to install the valley was to always install the lower and smaller roofs first and then the main roof over that and cut the CA cut into the main roof, based on the simple concept that water runs downhill. But I’m having a hard time finding documentation to support this.

Thoughts on this? Is this something I should continue to point out? I’m getting a lot of resistance from the roofers to fix this for homeowners, even though they often have one dormer installed correctly and one incorrectly on the same house or neighboring houses.

Ryan Schmidt
Certified Professional Inspector
Broadneck Home Inspections, LLC
Home Inspector | Annapolis, MD | Broadneck Home Inspections, LLC

Ryan please go to Control Panel top left and put in your information Thanks … Roy

Adding my contact info because it was not set up on the forum

See page 103, in the upper right of the circle diagram:

It gives you something to point to if you find that the valley is in such bad shape that you recommend replacement.

In any case, I would comment to the buyer that it is installed wrong but probably won’t be changed. One can peer under the cut to see if it is sealed, also, and seal it as a possible maintenance/preventative measure item.


I advise the client that it’s improper and document so in the report, however, I advise them not to push to have it corrected. The contractor is far more likely to create a problem than prevent one by redoing the valley. Let the client document to the contractor or builder that there is a workmanship defect so that they can come back to them if they ever have a problem with it.