Here’s how to get a warm, dry basement floor over a concrete slab when converting your basement into living space. Lay four-millimeter polyurethane sheeting across the entire floor, overlapping the sheets by about a foot. Then lay pressure-treated two-by-fours on the flat around the perimeter. Lay more two-by-fours, 16 inches on center, securing them to the basement floor with concrete nails. Fill in with one-inch rigid insulation and cover with three-quarter-inch plywood. Now you’re ready to finish off the basement floor with the flooring of your choice.
For more on flooring, consider: