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Warning: A building inspector in Phoenix told me my vapor barrier seams were 'just for show' last month.
Honestly, after he pointed out the lack of proper tape and sealant on a 15,000 sq ft slab, I switched to a 6-inch overlap with double-sided seam tape and now I check every single joint myself.
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umac712mo ago
Good on you for fixing it, but a 6-inch overlap is overkill for most vapor barriers. The standard is usually a 4-inch overlap with proper tape. Double-sided tape is solid, but you gotta make sure it's the right kind for the plastic you're using.
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diana1552mo ago
Guess my vapor barrier is just built different, like a luxury sedan with extra seams. Gotta have that six-inch safety net for when the house decides to start sweating. At least the tape bill will keep me humble.
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and honestly after i had to rip up a whole section of my crawlspace because the old tape let go, i went with the same 6 inch overlap setup. the double sided tape i used was the butyl kind, not that cheap acrylic stuff, and it's held up through two humid summers with zero peeling. i also started doing a visual check every spring, just a quick flashlight sweep after a heavy rain. it's probably overkill like you said, but my sanity is worth the extra tape cost.
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