I am renovating a 750 sq.ft., 45 year old cabin, built on slab on grade, in seasons that range from 100 above to -35 degrees F. The slab was cracked and broken up badly. After jacking & levelling the walls, I trenched around the perimeter, installed footings & pilings; then placed treated 5/8″ plywood from the bottom wall plate, to 3 ft. deep. On the plywood I glued 2 in. thick styro foam insulation and over this placed  vapor barrier and backfilled. This should solve frost and moisture problems. Inside on the old floor, wire mesh and rebar were placed and new cement poured (two1/2″to six1/2″ thick).    The floor will crack again and moisture may become a problem in the future.                                                                                                                          My question is: Should I place vapor barrier on the new cement before I place a 5/8″ plywood subfloor down and then the underlay and laminate flooring? The manufacturers say, “Yes”, but some sources say, “Definitely not!”.