TOPIC: I Have An Existing Metal Roof and Have A Question
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I have a large single slope metal roof that has been installed in the following order: Rafters, Purlins, Metal roof.
I want to fix this roof so that I can use the structure as a cabin and I want to keep the rafters exposed to the interior. My plan is to pull up the metal and add osb underlayment and felt paper and then replace the metal.
My questions: 1) will this stop the condensation? 2) there will be no room to vent (unless there is a way to vent under the Purlins that I am unaware of) is this ok? 3) I don't plan to add any insulation (remember I want to leave the rafters exposed which will also leave the Purlins and underlayment exposed but I'm ok with that) is this ok?
Thanks Jeremy. Where are you located? This will be a heated structure? What you're proposing will likely be a high risk for condensation on the underside of the roof deck. Some combination of insulation and/or thermal break on top of the roof deck is probably required unless this is in a very warm and dry climate.
I am near Athens Georgia. I've kinda switched gears on the project. My plan now is to add ventilation between the rafters and NOT leave them exposed. So my plan is from the top down... Metal roof, synthetic underlayment, osb, purlins (only because they are already installed) rafters, leave an airspace between the rafters, drywall. I will have vents in the eaves on both ends of the shed roof.
I believe the underlayment and ventilation should correct the condensation am I correct?
Oh and we wanted to do a wood stove for heat. The pitch is 3:12.
This sounds like a very good plan. I think you're fine without it but the only thing I can think of that you may want to consider would be a vapor barrier, such as a layer of polyethylene, behind the drywall.
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