Avoiding Moisture in Stud Bays
I’m remodeling a 40 year old cabin in East Texas (Zone 8). The cabin previously didn’t have insulation in the walls and the interior space was previously unconditioned. The exterior is cedar board and baton siding with roofing felt used as a WRB. There is no sheathing under the WRB. I’m going to fill the stud bays with rockwool. We’ve decided to use pine shiplap on most of the exterior walls. I’ve seen 1/2 in gypsum board recommended between the studs and the shiplap interiorly. Could thermoply be taped and used in lieu of the gypsum board? I’m wanting to make sure I don’t trap moisture in the stud bay. Thanks for any input. ST
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Replies
You'd normally want to put a layer of drywall up in the usual way, over the studs on the interior, then install the shiplap over that layer of drywall. The layer of drywall acts as a air barrier, so it needs to be taped and mudded, but not fully finished. I would recommend priming it though, just in case you want to do anything differently in the future.
It sounds like you have a reasonably vapor open exterior, so you would have outward drying. You'd need an interior side air barrier, and I'd recommend a vapor retarder as well. You could use something like CertainTeed Membrain here detailed as an air barrier, but it will be easier to damage than a layer of drywall would be.
I'm not clear if you're asking about using thermoply on the exterior or the interior? I'm not sure why you'd want to use that on the interior, but it could be added on the exterior.
Bill
Thanks, Bill. I was thinking about using it interiorly for an air barrier since it's something I can install myself. I wonder if the outward drying would be enough to let the stud bays breath. Thanks for your input. Appreciate it!
Sean