Ok, I've search on here but can't find the answer to my question. If there is another thread on this, please post a link and accept my apologies.
I'm replacing the laminate flooring in my downstairs, which is on a slab. It's above grade, slab is in good condition, but the laminate floors are moving quite a bit and some buckling has occured, and the cracks spread and close all year round.
My approach was going to be (after pulling up all flooring) put down a vapor barrier, then lay sheets of 1/2 plywood down, then underlayment, and go with engineered flooring (floating) . My thoughts are the plywood would help keep the flooring away from the colder slab and reduce the expand/contract of the flooring. And it sure would help warm the floor up some, it's freezing in the winter

So would this be an ok approach? Do I need to nail down the plywood or would it be ok to just lay it down and let it "float" too?
again, a link to what I've been missing, or some advice please?
Thanks