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1/2" nontoxic underlayment suitable b/w slab and floating cork?

mistertheplague's picture

I'm stumped. I have a section of floor (about 7'x10') that I need to raise just half an inch to be able to hit level with the other flooring I want to lay almost 400sq ft of floating cork planks on. I have a baby in the house, so using something that does not emit chemicals into the air is especially vital to me.

heres my dilemma. I'm on a concrete slab, trying to raise it to meet tile that is already laid and that I really don't want to take up because of the mess and noise (due to aforementioned baby). This is where the half inch comes in. I can't just lay plywood, since everything I find indicates that plywood underlayment a need to be over half an inch thick. The Eco friendly vapor barrier underlayments I see are only about 1/8" thick though. I considered a concrete underlayment self leveler like ardex and then saw how toxic it was and decided that is also a no go. It's looking like I'm stuck jacking up about 300 sq feet of tile so that I can start fresh, but I thought I would check here first in case someone else had an idea for me. The trick, obviously, is the combined need for thickness, vapor barrier, and indoor air quality. I know it may be an impossibility, but I am hoping I'm wrong.

mister (post #209547, reply #1 of 2)

Check into Homasote and it's properties.

edit:  Or 1/2" cement board, or two layers of 1/4" cement board.

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When only used as a spacer it (post #209547, reply #2 of 2)

When only used as a spacer it doesn't matter how thick plywood (or another sheet good) is, so long as it provides the intended spacing.  You only worry about the thickness when you need stiffness for, eg, ceramic tile, or if a nailing base is needed.

You DO need to worry, though, what you put over a concrete slab -- generally regular untreated plywood (or other normal wood-based sheet goods) would not be recommended for an on-grade or below-grade slab.

But if you can't use anything else a plain cementitious product should be fine -- it would only need to be self-leveling if you don't think you can screed it well enough.  But I looked at the Ardex MDS and I don't see anything alarming there -- it's only hazardous as a dust, and so long as you don't kick up much dust while mixing it there should be no problem.  Once mixed with water it's quite safe, unless you eat it.

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