steve valiquet
Hi. I recently had a metal roof installed. The contractor installed the roof directly to the asphalt roof. No vapor barrier, no strapping. When the roof was sold to me I was told that strapping the roof could cause damage during a wind event therefore they don't use it. I spoke with the manufacturer and looked at their product manual and I was told differently. Evidently when the roof expands and contracts it will eventually scratch the underside of the panels and cause rust/ rot which would not be covered under the manufacturer's warranty. Also my home is an A frame Chalet type home with a prowl roof. because the roof essentially runs by the deck it creates a cut hazard as there are sharp exposed edges at deck level. When I asked the contractor about this he insisted that was how this roof "imperial rib" is and cannot be addressed. The manufacturer had some small suggestions to offer without any clear cut answer. If you'd like pictures to explain what I'm talking about let me know. Your help is much appreciated.
David Stermer
Steve, Thanks for the question. I understand the concern of the existing shingles scratching the back of the new metal panels. My recommnedation is to install 30# felt to address the concern. However, I have never seen panels that actually failed from this. Typically, residential roof panels are relatively short and do not experience much thermal movement. Further, wood framing (commomn in residential construction) is somewhat flexible and can accommodate some thermal movement. With regards to sharp edges exposed to a deck area, the installer should provide a safe install free from hazards in habitable spaces. Regards, David Stermer

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