AboutBrad Zacharia Expertise All aspects of residential Roofing. This includes shingles and flat (low slope) roofs. I have knowledge in the installation as well as the design of roofs from an engineering standpoint.
Experience I have been doing roofing for 40 years. This was my father's business and I took it over in 1980.
Publications I have written responses to artcles that I felt needed a response to and those responses have been published in roofing trade magazines.
Education/Credentials BSEE Drexel University
www.ZachariaRoofing.com
This GAF cap has 3 layers, the top one being 4" wide...
It seems to me, if they are installed on a ridge, the top layer will cause the cap to tilt BACK running water under the next cap?
The design makes sense on a hip, but a flat ridge? Should I remove the 3rd layer?...or am I just being paranoid. http://www.gaf.com/Content/Documents/20605.pdf
ANSWER: Ridges can't be flat or they will leak whether it is 1 layer or 3 layers. You have something wrong with your roof if it is a flat ridge.
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QUESTION: Sorry, I didn't express it well. The ridge is HORIZONTAL, as opposed to a hip angle. My concern is that the the added 3rd (top) layer will cause the water to flow back under the ridge shingles.
The pitch is 6 and I'm applying them over Owens Corning VentSure Rigidroll.
I have only ever used trimmed 3 tab shingles before, never a built up product such as this- hence my concern
Thank you very much for your time and input. I look forward to your experience.
Answer Water will run downhill. If you have 50 layers and they all point downhill the water will just drip past each layer and run off. The only way it will run under a layer is if the layer is not downhill. If the top layer is not downhill then all 3 layers are angled the same and all 3 layers are not downhill. If that's the case then even if you had one layer the water will run under it. The ridge caps are supposed to be rounded at the top and go down each side. The water will run down the slope but even if it got a little under any of the layers it would have to run 6" horizontally just to get to a nail hole and that's not going to happen. In fact, the shingles themselves have cut-outs that water will get into but comes out the bottom of the shingles so water does get into shingles. It just should not get into it far enough to find an opening.
