Rigid Foam Under Subfloor

Lay sheets of high density rigid foam over the polyethylene.

Rigid foam under subfloor.

Since the weight it distributed throughout the 4 legs it will still be able to float normally. The right kinds are even dense enough to support a plywood subfloor without any supporting wooden strips underneath. Rigid foam is a nice option because it provides an excellent thermal break between concrete and flooring. Foam board insulation is used on attics and walls yet it can also be used to insulate your floors.

Provide a flat level surface for the finish flooring. Use a utility knife to cut the foam to size a hacksaw or drywall saw also work well for this. Tape the seams of the foam panels with heavy duty construction tape. One install was 4 of blue foam with woven wire mesh and radiant floor heat with 3 of concrete first and 2 of bluestone and setting bed over it.

Basement subflooring has so many jobs at hand. Most people do not think about insulating their floors unless perhaps it s their attic floor. The top layer of subfloor steps back and gets a layer of peel and stick flashing tape to form pan flashing under the sliding doors. You simply lay sheets of foam on the basement floor then fasten 5 8 plywood on top with concrete screws driven into predrilled holes in the floor.

Rigid foam insulation. Thinking outside the slab one solution would have been installing rigid insulation under the slab turning it up on the perimeter to form a giant pan and then casting the concrete slab inside the pan. The other was 2 of blue foam over a concrete slab with a layer of 2 x2 squares of osb with plastic dimple board as a floating floor over the foam. Lay rigid foam.

Unlike above grade sub flooring basement sub floor has to do all of the usual things and more. But insulating your floors is a good idea for many reasons including energy efficiency and height adjustments. Leave a 1 4 inch gap around the perimeter.