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I swore by a 6 mil vapor barrier for years, but a wet slab in Tacoma changed my mind | Flooring Installers - Thought Shares

vera_lewis2•6mo ago

I swore by a 6 mil vapor barrier for years, but a wet slab in Tacoma changed my mind

Had a job there last fall, concrete felt dry but the meter read 85%. Old me would have rolled out the thin stuff and hoped. New me uses a 10 mil reinforced sheet with taped seams every time now. That Tacoma house would have been a callback nightmare. What's your go-to for a high reading on a slab?

4 comments

4 Comments

vera_johnson96mo ago

Oh man, that hits home... I used to be the king of "it'll probably be fine" with the cheap stuff. Learned my lesson the hard way too, but with a basement that smelled like a swamp a year later. Now if the meter even blinks funny, I'm grabbing the thick stuff and enough tape to wrap a bus. That extra time and material is nothing compared to fixing a failed floor.

elizabethmason6mo ago

Wait, you actually had a basement that smelled like a swamp? That's wild, I can't even imagine dealing with that. What did you even do, just start over completely? I get being careful now, because that sounds like a total nightmare to fix. Once you've been through something that bad, you never want to cut corners again.

sethm466mo ago

Remember that musty smell after a heavy rain?

the_anthony5mo ago

vera_johnson9 said "if the meter even blinks funny, I'm grabbing the thick stuff" and that's exactly where I landed too. But here's something nobody's really talking about with these wet slabs and vapor barriers. I had a job in Portland where the meter was screaming high, so I went with 15 mil and taped everything like crazy. Turned out the real problem wasn't moisture coming up through the concrete, it was the slab sitting on a gravel bed that had a hidden spring underneath, basically a constant water source. All that heavy plastic just trapped the moisture underneath and it wicked up through the slab edges into the walls. So now I always check what's below the concrete before I seal it, not just the reading on top. Sometimes your vapor barrier is fighting a losing battle if you don't handle the water source first.