Things You'll Need:
- Polystyrene foam board
- Plywood
- Polyethylene tape
- Screws
- Screwdriver/drill driver
- Oriented strand board (OSB) with foam board backing
- Hammer
- Tap block
- Shims
- Plastic subfloor
- Heavy duty drill
- Masonry bits
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Step 1
Calculate the square footage of the area to be covered. Purchase the amount of polystyrene foam board needed (1-½ inch thick). Lay foam board on basement floor, taping the seams with polyethylene tape. Cover the foam board with ½-inch sheets of plywood, staggering the seams. Do not have the seams in the plywood the same as the seams in the foam board. Drill screw holes through both the plywood and foam board into the concrete 2 feet apart. Drive screws by hand or with a drill driver. Install the flooring of choice over the subfloor. This type of subfloor increases the thickness of the floor by 2 inches; check that ceiling height clearance will be acceptable.
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Step 2
For OSB board with foam board backing, install the inter-locking tongue and groove sections of 2 feet by 2 feet OSB board foam-side down onto the concrete floor. Lay the first section with the tongue toward the wall. Insert the tongue of the next piece into the groove of the first piece. Tap the sections into place using a block and a hammer to ensure a tight fit. Use shims furnished with the subfloor to level. This subfloor floats, allowing for movement from temperature changes. Install the flooring of choice. This subfloor adds 1-¼ inches to the height of the floor.
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Step 3
For interlocking plastic subfloors, snap the sections of subfloor together by placing the prongs into the holes on the next section and pushing down. The construction of the squares (2 feet by 2 feet) forms an overlapping seam when snapped together. The bottoms of the sections have dimples to allow air circulation. Use a circular saw to trim any perimeter pieces to fit. Use shims to level sections where the concrete floor dips or rises. In the event of a water leak, this subfloor can be lifted by unsnapping and reinstalling after the leak is corrected. Screws driven through the plastic subfloor around the perimeters hold the subfloor in place. This subfloor adds ½-inch to the height of the floor.
