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I used to think a 6 mil vapor barrier was fine for basements, but a job in Seattle proved me wrong.
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shane_anderson6mo ago
Wait, you were using a 6 mil in Seattle? That's asking for trouble. The ground is basically a sponge up there all winter. I saw a basement with a 6 mil barrier that looked like a waterbed after one wet season. It just can't handle the hydrostatic pressure, it gets tiny pinholes you can't even see. You really need that heavier stuff, like 10 or 15 mil, for any real damp soil. Anything less is just a temporary fix.
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fiona_nelson514mo ago
Even with a heavy mil barrier, you're still going to have problems if you don't put in a proper drainage mat or gravel layer underneath. Vapor barriers just slow moisture down, they don't stop it completely. All that pressure from wet ground has to go somewhere, and without a way for it to drain away from the membrane it'll just push through eventually no matter how thick it is.
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briannguyen6mo ago
Maybe it's just me but @shane_anderson, is a 6 mil really that bad? I've seen it hold up okay in some spots.
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