Return to Installation
Return to Forum
I’m building a 36 x 44 garage with a 4/12 pitch. The garage will be insulated and have heating and cooling. Most people in my area install 2x4 strips that are 2 ft apart on the trusses, then bubble wrap on top of that. Then screw the metal to the 2x4 strips. Should i use an under decking such as 7/16” osb, then 1x3” strips spaced 2 ft apart with bubble wrap in between strips? Any advice is appreciated. Thanks.
I do not suggest installations without decking over conditioned spaces, especially when the conditioned spaces are not real large. The risk is condensation. If the attic has ventilation or if the insulation is closed cell foam, you will be fine with decking and underlayment and no battens. Otherwise, battens are probably a good idea as well and battens can always help some with energy efficiency.
The place i called about metal from said they figured in a ridge vent if thats what you are meaning about ventilation.
What should I use for underlayment? And do you think 1x3” boards as battens spaced 2 ft apart will be ok?
A ridge vent functions as attic exhaust. You also need in take vents, usually in the eave overhangs / soffits. Much of the industry has gone toward premium synthetic underlayments. Something else could be required by code in your area such as a fire rated underlayment or ice and watershield on the roof perimeter and valleys. The batten spaces, should you go that way, needs to come from the roofing manufacturer as it needs to comply with how their product has been designed and tested.
I will have vented soffit as well. The underlayment that you are talking about, would they have something like this at lowes?
Yes, they would. You're not the Derek Hines who is a UMC pastor, are you?
Nope thats not me.
So if I solid deck with 7/16 osb, then put battens over that, wont the battens act like a dam if the metal does condensate?
Yes. However, the risk typically isn't that of condensation on the back of the metal if you have decking in place. Where the condensation would occur is on the underside of the roof deck. The battens though will prevent cold from transferring as much from the metal to the decking, and that helps prevent the attic condensation. In your case, because of ventilation in the attic, you will be getting the moisture (which originates inside the home) out of the attic, preventing it from condensing. Again, with attic ventilation and decking, I see no need for battens. That said, if you use battens, I would not expect any problems other than they make the roof harder to walk, they raise the level of the roof which can impact gutters and dormer windows, and they can lessen wind resistance of the roof. Give me a call if it would work better to talk this through ... 1-800-543-8938 ext 201.
I'll give you a call. What hours can I call?
I am normally in the office 8 - 5 except the noon hour, Monday through Friday, Eastern time zone.
If you would like to reply to this thread, please
If you do not have an Ask the Experts forum user account,