PSA: I was wrong about skipping moisture barriers on concrete

I always skipped adding a moisture barrier on concrete slab jobs to save time. But after a client's laminate floor swelled up from moisture, I read up on it and saw the science. Now I'm curious, what's your go-to method for testing slab moisture before install?

3 comments

3 Comments

nina_jenkins1mo ago

My friend Mike in Toledo had a warehouse job where the concrete felt damp. He used those moisture test kits with the discs, but they came back low so he installed vinyl plank without a barrier. Big mistake, the planks warped within a year from the slab sweating. Now he rents a meter to check the moisture right in the concrete, drills a couple small holes to get a real reading. He won't start a floor without that step anymore.

xena_fox391mo ago

My old flat in Phoenix had a slab that felt fine, but we used the calcium chloride test and it showed low. The bamboo flooring cupped anyway. Now I only trust a digital moisture meter for concrete, the kind you push pins into the slab. Why trust a kit when you can see the real number?

irisjenkins27d ago

That point about seeing the real number hits home. I was all about the calcium chloride tests for years. Then I had a vinyl job fail because the kit said it was dry but the slab wasn't. Now I use a pin meter every time, no exceptions.