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vapor barrier under platon subfloor?

magenta1295
9 years ago

Hello all,

I posted a message earlier this week regarding covering a concrete slab with a dimpled membrane and then laminate floor. i appreciate the responses to my earlier questions and concerns.

I have a new question and hoping someone can shed some light.

The concrete floor is currently covered in chipping epoxy paint, under which is possible asbestos black mastic. The area is 230 sq feet, and a small area (probably 3'x4') tends to get moist and the concrete looks dark. I am assuming the moisture is creeping up from the ground. The worst its ever been is some droplets, never a puddle. I keep the humidity at 55% via a dehumidifier.

As a temporary measure (two years ago) we laid a poly sheeting(not sure of mil) and on top of that RAM board (very heavy paper) until we could lay a floor. This spring I looked under the paper and saw that beneath the poly there was some condensation (not puddling) in the moist area. It is not within our budget at this time to address the moist slab.

Here's my question/concern:
Is it necessary to pull up the poly sheeting before we lay the dimpled membrane (Platon) and the laminate floor? Is it better for the poly to be removed or is that an unnecessary step? I initially planned to pull up the poly and wash the floor down. Once dried we would put down the dimpled membrane. If we leave the poly would the condensation be trapped there perpetually or can it migrate back under the slab? And if the condensation remained would it grow mold despite lack of oxygen under poly? I know once the dimpled membrane is put down there will be a thermal break, I'm not sure if that will help with the moisture coming up.

Thanks to anyone who took the time to read this and give advice!!