I am going to install engineered hardwood floating flooring throughout my home in SW Florida. Part of the house had carpeting, the rest has ceramic tile. We removed the carpet and there is concrete underneath. The tile is 3/8” higher than the concrete. I am trying to decide if I want to put plywood or cement board over the concrete to make everything the same height. I am worried about the moisture in Florida. Any thoughts? I plan on putting a moisture barrier over everything as well.

I removed the old laminate flooring from my kitchen and the dining room to replace it with vinyl plank. When I took up the quarter round at the kitchen cabinets I noticed that there looks to be a layer of OSB under the lower cabinets that does not extend throughout the kitchen. Everything else is just a layer of plywood. I'm assuming that the previous owner removed the OSB layer in order to have a continuous flat surface from the dining room into the kitchen to lay the laminate without a transition. The edges of the OSB are jagged, leading me to believe they just broke it off to remove it. 1. Will it cause an issue if i leave it this way when I lay the vinyl plank? Or do I need to reinstall OSB through the entire kitchen? 2. If it's necessary to reinstall the OSB, what's the best way to level it all to eliminate the need for a transition? Do I need to put OSB through the entire dining room as well?