You have a fairly simple one to fix. You need some floor stone.
Here come the choices:
gypsum based / cement based / self leveling

I prefer cement based products as they are not affected by water
and there are no incompatibilities with adhesives.

There are several manufacturers. Here is a good one:
http://www.mapei.com/MapeiAmericas/e...ucts_line3.htm

(top posted for your convenience)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Keep the whole world singing . . . .
DanG (remove the sevens)




"fh101" wrote in message
...
I recently moved into a second story condo and have encountered
what
might be a serious problem. When I was looking at the condo, I
noticed a gradual dip in the middle of the carpeted living room
(approximately 10' X 10' and perhaps 1 inch deep at the center).
We
hired a building inspector to check it out and were told that
the
plywood floorboards were slipping due to settling, though the
condo
was structurally sound. He also said that this could easily be
fixed
at a minimal cost by pulling back the plywood and reinforcing
the
frame with some 4X4's. Well, today I peeled back the carpet to
take
a look and discovered that the subfloor isn't plywood, it's
concrete!
What the ?!?

Anyways, the condo is about 20 years old and the previous owners
assured me that the dip hasn't increased in the past 6 years or
so.
Assuming that the frame is in decent shape, what would be the
best
(and most economical) way of leveling the floor? I only plan on
living here for another 3-5 years and don't want to spend too
much in
improvements. At the same time, I'd hate for my floor to
collapse
onto my neighbors downstairs. Any advice? Thank you in
advance.