my "old house" was built in 1873 and i'm looking to install a subfloor. the current floor is hardwood (which is unrepairable) and dips in spots and is very uneven. there is not a subfloor, the floor boards sit directly on the floor joists and so, i was wondering the best way to install a subfloor that is solid and level over the existing floor without ripping out the hardwood floors... (and i have a feeling shims won't be enough).. thanks