I bought a 65 year old house a couple years back (1100 sf, 2 story Georgian). This house was either built right at the end of the war, or right after that. When we bought the place, everything looked to be in great shape (walls weren't cracked, trim looked nice, new windows already installed, new furnace, new roof, etc.). The house had hardwood floors that, while worn and used, looked good but squeeked EVERYWHERE. Being as this was my first house (and the home inspector never brought it up as an issue), I chalked it up to being an old house that creaked. After living there for the last 3 years, I have come to find that the floor was installed in a way I have NEVER, NEVER seen before. Pulling up a HVAC return vent (large one), I could basically see a cross section of the floor. There is a wood slat subfloor (looks like about 10"-12" by 1/2" maybe, they are not all the same size...) that is mounted to the joists. On top of that, it looks like they laid maybe 3/8" to 1/2" thick, 1" to 1 1/2" wide furring strips at maybe 12" centers on top of that. Then, they put the hardwood floor (3/4") across that. This is so bad that when you walk across it in bare feet, you can feel the hardwood deflect. The wood has also began to separate from each other (at the tongue and groove seams). I still can not wrap my head around this or for the life of me figure out how ANYONE could think it was a good idea to install a floor like this. Now, I'm left to try to repair this mess. Being as these are mounted to furring strips, I have no idea how the floor is actually nailed down as the majority of the area underneath the hardwood is a 3/8" to 1/2" air gap (in the small area I could see, I did not see any nails protruding). So, I figure I have to:

1. Remove all shoe and base molding.
2. Gently pry up the hardwood (I REALLY want to try to reuse the existing floor) and number it as I take it out (so that I can put it back again)
3. Remove the @$*# furring strips!
4. Install a 1/2" to 3/4" plywood subfloor.
5. Reinstall hardwood floor

Does this sound feasible? Also, after thinking about this for a while, I think that the floor was added later in life, and the furring strips were used to level the floor. So, I'm assuming it's not going to be as easy as nailing down sheets of plywood on the wood slats. I'm assuming that I'm going to have to level the floor somehow. Any ideas as the best way to accomplish this? The floor joists appear to be 2x10s that aren't that evenly spaced (varying from 12 to 16 inch centers if I remember right) so I'm really not looking to be adding that much weight.

I just finished a portion of my basement, and think that this needs to be my next project as it HAS to be repaired. Any rough estimates on how long this should take?

I am looking for all suggestions (just keep in mind that I am going to be doing this all myself).

Thanks in advance.

If it were my house or I was called to remedy the problem, I'd do exactly as you have said. I would remove the old flooring, being careful not to damage the bottom of the groove. (they tend to want to break rather easily if not carefull) Pluss the flooring may be dryer then it should be causing it to be more brittle. Remove old furring strips, check floor for level and shim as needed and install 3/4 plywood, glued and screwed and reinstall flooring..