How To Insulate A Floor Over Concrete. Be sure to fix any problems in the concrete floor such as cracks, spalls and water problems. One option for insulating on top of a slab is to apply rigid foam insulation directly to the slab, then install the subfloor on top of the insulation.
This method is simple, but it has. The plan is to hang 2×10 joists (using ledger board and joist hangers) 1.5″ above the foundation perimeter so that the floor will be at the same level as the rest of the house. The columns sat on raised bases on the concrete slab, and the crew had to cut and fit around them.