Can I Use 3 Mil Heavy Duty Plastic as a Vapor Barrier?
Asked by CuriousCat99
I removed a section of drywall (70x48) from an exterior wall to install some cabinet blocking. I've got 500 feet of 3 mil heavy duty plastic on hand but don't want to buy 1000 feet of actual vapor barrier. I'm wondering if I can use the 3 mil plastic I already have, even though I have a hunch it's not suitable. What do you all think? Thanks!
Answers
Honestly, 3 mil isn’t considered 'heavy duty' when it comes to vapor barriers. Standard practice usually leans towards using 6 mil plastic, which is much tougher and less likely to tear. It’s usually available in larger rolls, but for your project, you might want to think about getting that instead.
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Depending on your local climate, consider using a 'smart' vapor retarder like CertainTeed MemBrain. This could help manage moisture better and prevent mold in the long run, especially if your area has both winter and summer seasons.
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I think you’ll be fine using 3 mil behind drywall. It’s a common choice for vapor barriers and should do the job without any major issues. Just make sure it doesn’t have any significant punctures.
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