Roof underlay

I went and got a quote for a metal roof yesterday. I've got a house with straight gable roof 58' long and 17' wide. The attached garage is 52' by 15', and a 4/12 pitch. I'm looking at strapping 1x4 over the existing shingles and putting the metal roof over that. After compiling my material list, the guy handed me the quote. I noticed there was no underlay listed on there. I pointed this out, and he replied something like "you don't need an underlay anymore. If anything, most people are just using a house wrap, like tyvek." Correct me if I'm wrong, but I feel this guy is out to lunch. First off, "no underlay anymore." Last I checked the principles of fluid dynamics and ice damming don't change. Everything I've read online and have been told indicates that a proper underlay should be used even when installing a metal roof over existing shingles. Am I right? Or is tyvek an affordable alternative to this? THe underlay looks to cost about 800 bucks for my roof. In my mind that's peanuts to ensure a leak free, ice dam free roof. Just looking for some input, as using building wrap seems inadequate to me, and it's the first I've heard of it. THanks		Guest User 7/15/2015	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/20562/find/
by leaving the existing shingles on that will be your underlayment. if you are having problems with leaks I would recommend that you remove the shingles; repair any damage to the plywood; install new underlayment, including a peel and stick along the eaves. I also recommend that you use products that are manufactured by a member of the Metal Roofing Alliance as we have agreed to certain minimum quality standards. After all same as everything in life there is bad, good, better and best. Thanks for selecting a metal roof.		Dick Bus 7/15/2015	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/20563/find/

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