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.
Certified Professional Inspector
Broadneck Home Inspections, LLC
Home Inspector | Annapolis, MD | Broadneck Home Inspections, LLC