Our front addition has a limestone slab porch (original to house) The slabs are probably 3' x 5' and 4 plus inches thick. The room has two air vents for heating and cooling but the floor/room gets very cold in the winter. The walls and ceiling are standard 2 x 4 w/insulation and very large windows. The limestone slabs have deep grooves in them which makes it very hard to clean as well. The drop off to the floor is about 5". I would like to know if I should build a floor over it and insulate the floor?( but only working w/5 inches) Or should i fill the voids in the limestone and cover w/concrete adding some type of heat to it or on top of it? Do you have any suggestions? We would really like to maintain the stone look along w/maintaining a warmer temp. Thanks!