roofing felt touching metal

jk pendleton
5/29/2017
ive gotten myself into a corner. it doesnt matter now how i got there, i am there. if i put 30 pound roofing felt directly under the metal roofing will it corode or in any way harm the metal? if so, should i seperate them with a layer of house wrap? thank you.
Todd Miller
Isaiah Industries, Inc.
5/29/2017
Being in Florida, you may know this, but underlayment must meet code and the product approval for the metal roof you're installing. 30-pound felt is a reasonable underlayment but, if you are installing a roof that has a lot of contact with the underlayment, you should use a slip sheet on top of the 30 pound felt. You could use a synthetic underlayment or something like red rosin paper.
Guest User
5/30/2017
i saw the red rosin paper and didnt know what it was for!
Brian Partyka
Metal Roofing On-Demand
5/30/2017
I'd stay away from Red Rosin paper....specifically in Florida...we had a conflict with red rosin paper under an aluminum metal roof where the pH level created an acidic environment and burned a hole in the aluminum panel. I'd recommend a synthetic underlayment.
Guest User
5/30/2017
what about tyvek house wrap between the tar paper and metal?
Brian Partyka
Metal Roofing On-Demand
5/30/2017
House wrap serves a different purpose than roofing underlayment....I would not recommend house wrap to be used as a roofing underlayment mainly for safety and most important long-term performance. Dupont makes a product in the Tyvek family called Protec 120 Roofing underlyment if you want to use a similar "product".
Todd Miller
Isaiah Industries, Inc.
5/30/2017
Thanks Brian. I had never run into that before on rosin paper!
Guest User
5/30/2017
thanks to all that have answered, but i guess i havent been clear with my question. imagine someone has a gun to your head. they have a roof already covered with 30 pound felt and a bunch of metal on the ground. they tell you to choose between putting the metal on the felt, touching, or to put something between them to keep them from touching. the gun is cocked. what decision do you make? do you put something between them and if so what?
Brian Partyka
Metal Roofing On-Demand
5/30/2017
There are a number of synthetic underlayments in the market...typically 1000 SQ FT per roll that can be nailed...impregnated asphalt felts are designed to "feed" shingles.....please refer to www.srui.org (Synthetic Roofing Underlayment Institute) for a list of synthetic underlyaments.
Brian Partyka
Metal Roofing On-Demand
5/30/2017
No worries Todd...it may have been an isolated design issue however the rosin paper was the culprit
Guest User
5/30/2017
sigh. im sorry but this is very frustrating. you guys are very smart and really know your field, i am sure of it. but institute white papers are not what i require. i just want to know if i need to put something between my metal roofing and my felt. all i want is a straight answer. no warranties or commitments. should i put something between these two materials???? even if its grocery sacks and sunday papers. thats all. i have what i have, im dealing with the situation i have created and am just trying to make the right decision going forward. i guess i will go hang out at the home depot parking lot and ask some roofer.
Todd Miller
Isaiah Industries, Inc.
5/30/2017
Thanks ... this thing has taken some twists and turns. Per my original response, though: if you are installing a roof that has a lot of contact with the underlayment, you should use a slip sheet on top of the 30 pound felt. You could use a synthetic underlayment or something like red rosin paper. So, the answer is "yes". I would not install a vertical seam panel direct to 30 pound felt in your area. Based upon subsequent responses, I think that synthetic underlayment would be a good option, either over the 30 pound felt ... or all by itself. Again, though, you will need to make sure that what you're doing meets local building code requirements as well as any special requirements under the Florida building product approval for the product you're installing.
Brian Partyka
Metal Roofing On-Demand
5/30/2017
Yes..use a synthetic underlayment over the 30lb felt or in place of the felt. Good luck

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