I was sure my garage floor was fine without a vapor barrier

I poured a new concrete slab in my detached garage last fall and skipped the plastic sheeting to save a few hundred bucks. This spring, I started seeing a damp spot in the same corner every time it rained. My buddy, who does foundation work, came over and just pointed at it and said, 'That's ground moisture wicking right up through the slab, man.' It finally clicked that the barrier isn't just for new builds, it's critical for any slab on grade. Now I'm looking at having to cut out and patch a 4x4 foot section to fix it right. Has anyone else had to retrofit a vapor barrier after the fact, and how bad was the mess?

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3 Comments

ryan_sanchez7mo ago

My old foreman used to call it the six dollar insurance policy. I thought he was just upselling until we had to tear up a patio slab for the same reason. The demo dust gets into everything, and matching the finish on the patch is nearly impossible.

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lindahunt7mo ago

Consider the noise and dust fines from the city. That cheap plastic sheeting never contains the mess, and a neighbor's complaint can shut your whole job down.

9

mila_anderson346mo ago

Man, that's a brutal lesson to learn the hard way. How big of a patch are you looking at cutting out? Ryan_sanchez is totally right about the dust and the finish. When we had to do a small fix like that on a job, the dust coated every single tool in the truck, and the new concrete never looks the same as the old stuff. It always ends up a slightly different color or texture, like a permanent reminder of the mistake. You'll be looking at that spot every time you walk in there.

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