We have a 114 year old house that we have been lovingly repairing and upgrading ourselves for 6 yrs. The floors are hardwood with no subfloor beneath. The floors were not level and sagging. We have torn out the old hardwood, repaired the floor joists and laid plastic and plywood subfloors in two rooms.Then installed new hardwood. Our bedroom floor is sagging due to the weight of 2' x 3 ' hearth that was built on top of the hardwood/sub with no support. The hearth has now been removed and it is a blank canvas to work with. The joists are good. What is the easiest way to level and prepare for new flooring, without tearing out,installing plastic vapor barrier & new plywood sub floor?? We've been told to use a self leveling crete. Is there another way?? Could vapor barrier be lain over the old hardwood, then level with varying degrees of thickness of plywoods? Is there a product out there to make this easier?? I hope so!