I'm installing partition walls in a garage to make a 10' x 10' office space. Rather than just the concrete floor, I'm considering laying down a 3/8" plywood floor and finishing that with vinyl tiles (self-stick). I'm trying to avoid the feel of a cold concrete floor. What I'm afraid of is that, unless I prep the floor surface, that in time I may have uneven seams where the plywood joins. Aside from carpeting, any ideas? Also, somebody suggested laying down a plastic vapor barrier under the ply...someone else said "no way, the concrete needs to breathe"...feedback?