Help needed with a floor issue

[jmc]

Long shot, but the distinct discolored/moldy square might have something to do with a wet area rug at some point, like from a commercial cleaning, that never had a chance to dry properly.

 

[EddieWalker]

I talked with my client yesterday and offered her a variety of options. She decided that she really didn't care if the vinyl planks were the exact same height in her bedroom as the rest of the house. So no plywood is being installed.

I'm removing all of the wood and the glue so the concrete is clean and smooth. Once that's done I will coat it with two layers of Mapei Aqua Defense. I'll let that dry over the weekend and then install the LVP over it.

 

[fatjay]

I installed it all in my basement. But I floated it. I put down clear 3mil plastic sheeting the entire concrete floor. Since concrete is pourous material, I didn't want any moisture coming up, even though the flooring says vapor barrier included. It's like $10 for 200 sq ft of plastic, just do it. Taped it in place and put all the flooring down. Never a moisture issue and my slab is a floating slab that lets water run under it to the sump pit.

Also the moment i saw your pictures, i said to myself he's never going to get that level again, you're going to have to redo the whole room, and those planks really are sensitive to off square/off plumb in my experience. I was glad when you said she didn't care if the flooring was not the same height in that room, saves you a lot of hassle.