Solid Hardwood, Engineered and Laminate Flooring - Subfloor question

Great forum. I am getting ready to install either a laminate floor or an engineered floor, budget will dictate which. In either case I am considering laying a plywood substrate to my first floor concrete foundation. The purpose for this is to eliminate have to prep the concrete for the incoming floor. Is this an acceptable measure, or am I better off leveling the concrete and filling in all the small craters that were created when I removed the tack strips for the old carpet. If this is the way to go, should I nail the plywood to the slab and if so do I need to allow for expansion and contraction of the plywood. Also, would the vapor barier go under the plywood, or between the plywood and the floor.

Thanks,
Collin

Your better off prepping the concrete, rather then trying to install plywood over concrete. You just think it would be cheaper.

To do it right, it is not cheaper, because your going to be making the concrete flat to accept the plywood without voids(same as you would under the flooring laminate or wood). Your going to need moisture vapor retarders, of asphalt mastic(glue) and roofing felt, along with plastic poly of 6-mil or greater.

There is more to it then just slapping a sheet of wood on the concrete.

Perry, I have noticed you do alot responding on this forum. Thanks for taking the time to help us do it yourselfers. Thanks also for the sound advice. I was wondering if my idea was half baked or a thought of genius. I guess I was half baked again.