Preferred and Recommended Method

Guest User
11/16/2015
I just bought a prefab camp and I had a contractor come up to install my wood stove. He saw, when he went through the roof, that the metal roof was just installed on the 2x4 rafters with no sheathing or vapor barrier. I contacted the camp contractor and asked why I did not have sheathing and vapor barrier and he replied "When you do metal roofing, the preferred and recommended method is purlins (2x4 horizontal on the rafters) to support the metal roofing panels. sheathing is generally used when you use shingles or shakes. the purlins raise the metal up off the insulation so that there is an air gap to eliminate condensation, because the metal is the same temperature it is outside. That's why the insulation is left down and not run up to it and in contact with the metal. The roof has venting the entire length of the building and there is no cause for concern." I guess my question is the current construction ok or should I hold final payment until the roof is fixed - this is not built to home construction but is a camp that will be year round.
Info @windowsonwashington.net
An informed customer is our best customer.
11/16/2015
Theda, The air gap is an acceptable method of laying down the roof but there should still be some sort of vapor control layer. It should be on the warm side (i.e. room side) of the home to prevent moisture from diffusing through the insulation and hitting the backside of the cold metal.

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