How to Insulate a Concrete Porch Floor

Take all portable items off of the concrete porch then clean the floor surface with concrete cleaner and a scrub brush. Spray off the concrete floor with a garden hose, after cleaning, to remove any dirt and cleaner residue left behind.

Measure the length and width of the floor. Lay a waterproof membrane over the concrete surface and cut as many strips, as necessary, to cover the entire porch, overlapping each strip by 5 to 6 inches. Peel the adhesive backing from each strip and press it down into place on the concrete.

Use the largest rigid foam insulation boards possible for the space without wasting any materials. For instance, if the porch is 5 feet in width, buy the same width of foam board so that you don’t have to cut the board down. Line the concrete porch with the foam boards and use a utility knife to make cuts through them if you do have to trim some pieces down.

Take the backing off of the foam boards, one board at a time, and press them down into place over the waterproof membrane on the concrete porch. If small spaces appear where the foam board edges meet, apply a line of caulk to these seams and smooth the caulk down so it doesn’t sit above the surface of the boards. Allow the caulk to dry for 24 hours if the temperature is warm or 48 hours if the temperature is moderate.

Conceal the foam boards on the concrete porch floor by painting them. If you prefer that the boards blend in with the concrete, use gray paint to conceal them.