Necessary to add strapping over smart vapor retarder
Hey All,
I’ve seen mixed info on this so hoping this group could help me out.
Details:
– Exterior air barrier is taped zip
– Cold climate zone 6
– As such, adding a smart vapor retarder interior. Majrex on the ceilings and membrain on the walls
– Electric is already roughed in and boxes will be fire caulked to prevent air flow through them
– A couple recessed lights at the ceiling plane will have air tight site-made boxes around them
So the question is — Can I attach drywall directly over the smart vapor barriers, or do I need to add strapping? I’ve seen it detailed in both ways. I understand the benefit of a service cavity with the strapping option, but if I don’t need that cavity, curious the reason for strapping from an air tightness and vapor retarding aspect.
Thanks,
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Replies
You can drywall directly over the vapor retarder. IF you are using the vapor retarder also as an air barrier, then the details at things like electrical boxes become much more critical. I presonally always detail the vapor retarder as an air barrier, so I seal the perimeter of the vapor retarder to the framing with sealant, and I tape it at all electrical boxes or any other penetrations. I'm not a fan of service cavities: I think they add a lot of construction effort for something that will probably never be used.
The vapor retarder itself doesn't need any strapping. If the vapor retarder is on a really long wall and gets annoyingly "flappy" in the middle, just add some staples to secure it to a few more studs to keep it under control. If you're really OCD about your details, you can tape over the staples to seal them.
Bill
Thanks Bill