Metal roof over sagging decking

We are wanting to put metal roofing over our existing shingled roof the problem I am seeing with our existing roof is that there are a few places where the decking sags up to 1 1/4" between the rafters, I was thinking about running purlins across the roof to attach the metal roofing to. I am also wondering should I put the underlayment under the purlins or on top of them?		Guest User 7/6/2017	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/22216/find/
In this case, the underlayment would go beneath the purlins. Yes, what you're proposing can be done but not all metal roofs can be installed over purlins. You would need to choose a product that can be installed on purlins. The purlin spacing would then be specified by the manufacturer. I hope this helps.		Todd Miller Isaiah Industries, Inc. 7/6/2017	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/22217/find/
That's what I was thinking that it had too, the metal we have chosen can be installed on purlins @10 inches on center. My understanding for the use of synthetic felt is to not scratch the metal and because of the heat properties transferred from the metal to the underlayment and regular felt won't hold up to the heat. But since there will be a 3/4" air gap between the metal and felt would regular felt work or do I still need to use synthetic udl underlayment?		John Cervenka 7/6/2017	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/22218/find/
I would still recommend the underlayment. Although not all people interpret the code the same as I do, I feel it is required by the International Building Code. Additionally, if you should have any water occasionally get underneath the panels, the underlayment will be a great safeguard -- and inexpensive.		Todd Miller Isaiah Industries, Inc. 7/6/2017	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/22219/find/
I understand using the felt is a good idea my question is will regular 30# felt be ok to use or do I still need to use a synthetic udl underlayment?		Guest User 7/6/2017	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/22220/find/
30 pound felt will meet code requirements ... and I would think it will be acceptable to your roofing manufacturer though you should confirm that with them.		Todd Miller Isaiah Industries, Inc. 7/6/2017	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/22221/find/
Thanks for the information. I will check with them.		Guest User 7/6/2017	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/22222/find/
I have a question but my sign in won't allow me to do it so I hope its ok to ask from here. Can you install a metal roof on a wet roof after it has been raining all night but not raining now?		Guest User 9/14/2017	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/22223/find/
Amy...that post has been answered. Please see here: https://www.metalroofing.com/v2/forums/index.cfm?action=mboard.members.viewmessages&ForumTopicID=9220&ForumCategoryID=62		Eric Novotny An informed customer is the Best Customer! 9/14/2017	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/22224/find/

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