I have a 92-year old house whose floors are very off-level, some as much as 2 inches. Just heard about this self-leveling cement which can be used to level floors but do not know what type of flooring it can be used on or the preparation required. The floors throughout this house are 5-inch wide pine boards which have been covered with carpeting. Could I use this stuff directly over these pine boards or do I have to put something over them before using it? Has anyone had any experience with this stuff? Any information would be greatly appreciated. The pine boards have major gaps in them.