Hi, Carmen, Now that you have all this information, add this to it as well. You can put in a new floor, as the others have said, using 2x10 or 2x12 timbers, but do not fix the new joists to the old (not toutching)you will be laying chipboard or plywood on top so you can give a little or take a little for the centers of the joists. all you have to do is make sure that the end of the panel comes onto a joist, the other two ( in the middle) joists you can cheat a little,and as the man said "if you have air ducts then remove/move/change them, but dont cut the joists. I can't say much, its already been said. John 2000.