Is OSB sheeting required?

Troy Szydel
2/23/2015
I am building a cabin that is 24x40 with an 8/12 pitch. I have heard different responses from everyone I've asked so here goes. I am using 2x12's to create a cathedral ceiling and I want to put on a metal roof, I am also planning on using spray foam to insulate this roof. I would like to attach a layer of typar on top of the 2x12's and screw the 2x6's for attaching the roof to on top of that. I would then attach the steel roofing to these 2x6's and once that was complete I would then spray foam the interior of the studs using the typar as the break from applying it directly to the metal roof. First is this feasible, do I need the typar as a break or do I really need to put the sheeting, tar paper and ice shield on prior to the 2x's? Thanks for any and all help.
Todd Miller
Classic Products, Inc.
2/23/2015
Troy, what you're planning can be done but make sure that the manufacturer of whatever metal panel you install approves its use this way. Generally speaking I am not in favor of "no decking" on residential installations but the use of closed cell foam takes away the condensation issue so then I am comfortable with it. I do like the idea of the underlayment so that, if the metal roof ever needs to be replaced, the foam is not directly adhered to it.
Troy Szydel
2/23/2015
Thank you, I thought it was doable but everyone had a different opinion, the underlayment is being used for what you stated. I also plan to put in a ridge vent so that any heat created by the roof can escape and not bake the insulation. Is this a good idea as well?
Troy Szydel
2/23/2015
The last one didn't work so I'll try again. I plan on putting in a ridge vent as well to let the heat that is created in the summer escape to prevent the baking of the insulation, is this a good idea
Todd Miller
Classic Products, Inc.
2/23/2015
Normally, when an attic is fully insulated with closed cell urethane foam, there is no ventilation. If you have a way to get intake vents as well though, and you can have good balance between the intake and exhaust (ridge) vents, I do not see any harm though.
Troy Szydel
2/23/2015
Awesome, thank you for all your help!!!!
KEVIN DUPKE
3/27/2015
Todd, per your above comment, is the only concern about a no decking with a metal roof and closed cell insulation directly on the metal is because of potential replacement concerns? Like Troy, I'm planing on a metal roof on steel truss /purlins with no underpayment but with closed cell spray foam directly to the metal panels. It's ok with the manufacturer. Importantly, we get a significant wind resistance additive effect with the closed cell contacting the metal roof. Any other concerns from your perspective? Thanks, Kevin
Todd Miller
Classic Products, Inc.
3/28/2015
Yes, the direct contact and how that will affect replacing the roof is my concern. That said, the insulation job needs to be well done to make sure there are no areas where moisture vapor might get through it.
Info @windowsonwashington.net
An informed customer is our best customer.
3/29/2015
+1 If you can incorporate some rigid foam to the underside of the purlins and encapsulate the area over the rigid foam, you will allow for future servicing and replacement of the roof at a later date without disturbing the foam.
KEVIN DUPKE
4/10/2015
Todd / Eric. Thanks for your "FREE" expertise. I'm very grateful. Eric, the only problem with using foam board √ľnder the metal, the foam spray will not make direct contact with the metal roofing. With direct contact, close cell foam can add 3-5 psi of additional wind resistance to a roof. That's significant down here in Cajun Lousiana, aka Hurricane Country. BTW, if you folks are ever down this neck of the Bayou, the meal is on us! Thanks, Kevin.
Info @windowsonwashington.net
An informed customer is our best customer.
4/13/2015
Kevin, That is true. I have never seen a metal roof stay down because of foam yet though. Doesn't mean it hasn't happened. If it is properly fastened, you shouldn't have an issue and thank for the meal invite. I do love me some crayfish.
Tooger Smith
4/15/2015
Kevin, at least we know that Eric Novotny is a "yankee" because he called them "crayfish". No Cajun would do that!!!! Good site tho!!
Info @windowsonwashington.net
An informed customer is our best customer.
4/16/2015
Tooger....that is an autocorrect fail from the browser. I would have called them crawdads myself, but make no mistake...I can eat those bugs with the best of folks.
Guest User
4/30/2015
I have a shingle roof at this time and is going to have it replaced with metal roof. I wont all the shingles removed, should i have a tar paper under lament put on before the strips and metal put on it. this is an older home built back in the 70's. I am going to have ridge vents put on when i have the metal roof put on. is there anything else i should have done, this is my first roof and am working with a contractor that has put them on before just wont to make sure he is advising me of what i need to have done.. any help would be really helpful. I am not that much into construction and not sure if i ask all the right questions...Thanks
Todd Miller
Classic Products, Inc.
4/30/2015
Underlayment is a must. Strapping is not required with all metal roofs and, assuming you have good attic ventilation, would not be necessary.
KEN TOOMEY
7/7/2015
Installing 29 Ga. 36" wide (4) 3/4" high ribs ,with underlayment on 1/2" OSB sheeting . We use (1) wood screw per rib across the sheet (4) screws. Location: near Flint michigan the questions are. 1- what should the spacing of the screws be length wise the sheet ? 2- what size should the screws be?
Info @windowsonwashington.net
An informed customer is our best customer.
7/7/2015
Who is the panel manufacturer? They should have explicit instructions on the panel that you would want to follow to the letter for warranty coverage.
KEN TOOMEY
7/7/2015
THANKS: GOOD IDEA. I called the panel roller- 12" spacing of the screws on the length of the panel. correction the 36" wide panel has (5) ribs not (4). KEN TOOMEY

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