underlayment?

Why do I need to put down an underlayment when installing a metal roof over old shingles? What are the negatives of not using an underlayment? thanks		Guest User 5/23/2013	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/18397/find/
This is required by the ICC and it's also a good idea to prevent abrasion between the asphalt shingle surface and the metal roof.		Todd Miller Isaiah Industries, Inc. 5/23/2013	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/18398/find/
+1 And it is really cheap and the last thing you would want to short cut on.		Eric Novotny An informed customer is the Best Customer! 5/25/2013	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/18399/find/
Thinking about putting on a metal roof on our duplex. It would be Mcelroy metal 29 guage kynar exposed fastener metal - max-rib. 2x4 and 1x4 will be placed on existing roof ( 1 single layer of shingles) then the metal will be installed with neoprene washered screws. My question is should there be any insulation between the 2x4 and 1x4 so that condensation does not form between them and cause the roof to rot. have been told that yes we need that so that the roof does not rot and no we don't need that because it can breath. If we don't have insulation we will have problems in years to come. Thanks for your help		Guest User 7/29/2013	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/18400/find/
The roof does not need to breath in this application and it will not breath through 1 layer of shingles. Is the older shingled roof vented? You will need to preserve that venting and allow for it to work with the new roof but the roof will not vent through the shingles on the old roof.		Eric Novotny An informed customer is the Best Customer! 8/2/2013	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/18401/find/

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