Roof unlayment for a unvented rood

Guest User
2/26/2008
I will be installing a standing seam roof on a home we are building in North Texas. I have read about the problems with felt paper sticking to the bottom of the roof panel and tearing. I have started evaluate alternative underlayments and read about Titanium UDL and Sharkshin- all of which state on their WEB site that they should be installed above vented attic spaces as they are considered a vapor barrier. The home we are planning will have a sealed attic with open-cell spray foam encapsulating the attic. The question I would like to pose is what underlayment options are there for an unvented attic? Thank you for providing information on this issue. Chapel
Guest User
2/26/2008
Chapel, Usually we use an ice and water shield or 30 lb. felt. Most felt is fairly dry and sticking is not a problem. Sometimes felt gets over saturated and then it will stick to the metal, shingles, decking or anything else it is in contact with. Where are you building in North Texas? The reason for the question is we are located in N. Texas. [email protected]
Guest User
2/27/2008
We are building in Southern Denton County in a Town called Copper Canyon. Other posts on this forum have indicated that when a standing seam metal roof gets hot, the felt will stick to the metal and since the felt has been tacked to the roof decking, it will tear. Chapel
Guest User
2/27/2008
Chapel, Most felts are pretty dry, but sometimes you get some that is saturated to the point it oozes asphalt. Felt like that does stick but I haven't come across any like that for a couple of years now. The dry felt we have hasn't been a problem, but there are other alternatives like the synthetic underlayments and the peel and seal ice and water shield. It comes down to the point of what you are comfortable with. We all have horror stories about things that went wrong from oil canning to condensation problems. It's a matter of persistence and experience to not have any issues. We are located in Decatur. [email protected]
Todd Miller
Classic Products, Inc.
3/1/2008
Thanks Wade. Chapel, for your specific application, I believe that the synthetic underlayment manufacturers would be okay with it.
Brian Selig
Architectural Building Components Metal Roof and Wall Panels
3/1/2008
Consider using a standing seam panel with an offset clip of at least a 1/4" off the deck. A slightly subspended panel will also prevent some radiant heat transfer. If you do choose to use a panel that is flush on the deck, Sharkskin Ultra can be installed without caps. I see that as an advantage. There are also several peel and stick membranes available with polyethylene faces like (I think) the Titanium comes with.
Leo B.
NewEnglandMetalRoof.com
3/5/2008
GAF make a great underlayment called GAF Deck Armor. It is our underlaymet of choice! It is breathable, and works much better than felt, ventilation wise. At the same time it is a waterproofing underlaument, so it will keep water out. I would not use sharkskin of titanium as the trap the moisture under between itself and wood, making it always "wet" sort of speak, especially when you spay insulation on to the back side of decking. Do not use Ice and water. Although it is supposed to keep water out, it might not stick to the wood 100% (especially the cheaper brands) and will also trap water underneath it. We only use I&W along eaves and valleys, which i think is also required by the Code around here, but never completely cover the deck with it. There is at least one more brand of breathable underlayment - it is bright green on the outside, but i'm not sure who makes it. And besides, that green one is VERY expensive, while deck armor is very reasonable. Also GAF has recently improved it - the made it thicke and more tear-resistant. Never the less, the earlier version was still very strong and impressed me a lot. Now it is the only one we use, and i've worked with many of them, including tri-flex, sharkskin, the one that was made by Elk, before GAF bought them out. Did not work with titanium, but basically it is a very durable tarp :) Good luck with your new home. Good luck
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