Installing plywood subfloor over concrete
I'm getting ready to install around 1200 sq ft of engineered wood in two areas of the house. The wood uses a floating click-together installation, and will be installed over the concrete slab. Being engineered wood, I understand it can go straight onto the concrete with a moisture barrier underneath. However...
Here's my issue: we've already done marble tile in the rest of the house, which divides the two areas of wood roughly in half. There are three transition areas where the marble is roughly 1.5" - 2" higher than the concrete the wood will go over. In order to minimize the height difference, I'd like to put plywood underneath the wood to bring the finished wood floor up closer to the level of the marble.
I'm thinking I can just line the concrete with 1/2" or 3/4" pressure treated plywood, then lay the moisture barrier over that and the hardwood on top. Any flaw in my plan? Should the plywood be glued to the slab (easier) or nailed (more difficult and time consuming) or both?
Any other tips for installation would be much appreciated as well!