Yes, you have a greater chance of condensation of the warm moist air in your attic reaches the back side of the metal panels than if it reaches the back side of the plywood decking. Please consider re-roofing as a time to increase the ventilation in your attic as well. Has your roofer presented you with an analysis of your attic's ventilation and even of the current moisture levels in it?
Todd Miller
2016-04-27 21:32:22.000000
I have an older home and am planning on having a metal roof installed. The roof I have now has cedar wood shingles under the roof. When that roof was installed 17 years ago, they just put the roof over the wood shingles. This new roofer says that they need to remove those cedar wood shingles. They can put the metal roof over it, but do not recommend it. Once they remove the cedar wood shingles, all that will remain are the 2x4's and some 1x4's that are installed horizontally. The roof man says that decking is not required or recommended because of the condensation it would cause. So, they will be putting the black tar paper and nailing or screwing the metal roof to the wood. Is this ok or should I insist on decking?
Christine Pacheco
2016-04-27 21:14:04.000000
+1
We need to know what the current ventilation of the attic is to start with. Soffits, Ridge Vent, Gable vent, etc.?
I would do an internet search on air sealing and insulation. This is unrelated to the roof directly but just a great idea from an efficiency standpoint and it will keep much more moisture out of the attic and mitigate the risk of condensation.
Lastly, solid plywood decking is always a plus if it can fit into the budget. It makes for a nicer installation as well as helps control the condensation potential again. Nothing about decking boards is wrong here though and many times they are of a better species of wood than we can get these days. A proper underlayment and ventilation schedule should eliminate any condensation concerns.
