Video on the cost of concrete floors. Depending on the level of complexity, concrete floors can cost as little as $2 to $6 a square foot or be as expensive as $15 to $30 a square foot. These applications can add another $2 to $3 per square foot to the cost of the floor. 2  Moisture-Vapor Transmission-Some floors have a high level of moisture-vapor transmission that will need to be remedied before most decorative coatings, overlays or sealers can be applied.