Rigid Foam Over Subfloor

Rigid foam is a nice option because it provides an excellent thermal break between concrete and flooring.
Rigid foam over subfloor. The foam butts against the mudsills for a complete thermal break. For your install plywood will work fine. Use t g and screw through the foam and the into original floor to keep the large sheets flat. You can use either one or two layers of plywood or osb and the subflooring can either be fastened to the concrete with long tapcon screws or it can simply float above the foam.
Expanded polystyrene eps extruded polystyrene xps and polyisocyanurate are the most used types of rigid foam insulation. Use a utility knife to cut the foam to size a hacksaw or drywall saw also work well for this. There are several ways to install subflooring above the rigid foam. Then i glued osb sheets to the foam board.
This will also help eliminate the hollow sound and feel the floor will have over the foam. Plywood screwed down through the layer below. Leave a 1 4 inch gap around the perimeter. I glued 1 inch thick rigid foam board onto the concrete floor which i had previously treated with a 1 16 inch coating of xyprex moisture proofing.
Tape the seams of the foam panels with heavy duty construction tape. Lay sheets of high density rigid foam over the polyethylene. If you choose to have a floating subfloor it s best to install two layers and screw them together. Proper subfloor for hardwood in a renovation.
Two layers of 3 4 inch osb subflooring then float unattached on top of the foam to provide a solid and stable underpinning for the wide board wood floors. Every 8 on the edges and 12 in the center.