Wood Flooring onto Uneven Concrete?

Question

We pulled out a wall shelving unit so the area would open. I understand we need to put down a membrane and then foam before the wood.

But the concrete is not even. It's very rough as well. Will the foam take care of leveling it? And even if so, will the pressure from putting our entertainment center on top press and maybe puncture the membrane via the rough concrete if something else is not done first?

So first, will foam do with a membrane for laying on concrete?

And second, what do we do if it ends up not leveled? What material would work good; set fast and strong to do the job? Some sort of glue maybe? A varnish? Rubber cement?

Answer 1

The RIGHT thing to use is a self-leveling concrete topping.  It's usually a watery-mix of cement and epoxy that is poured over the slab.  When it's cured you have a smooth and level surface.  This stuff is not cheap, but it will DEFINITELY work if you install it right.

Answer 2

1/8" difference in 3' is the maximum tolerance for unevenness Rough concrete isn't really a problem, nor does it matter if it slopes a little. If the floor has excessive dips and humps though, they need to be fixed. Major low spots are easily fixed by using a self leveling compound or a less expensive floor patch. If you are installing a floating floor, any cement, or thinset will work. I usually use Henry skimcoat&floor patch. If you need to fix a very minor low spot you can lay a piece of cardboard or a bit of an old shingle in the dip.

As for your membrane, you will need a foam for padding and plastic for a moisture barrier. Two in one products are not very effective. Install the foam first, then the moisture barrier. A 6 mil. virgin poly plastic is best. Overlap the plastic a few inches and tape the seams.

If you have any other installation questions feel free to email.