pictures to illustrate:
The house is in baltimore and was built in 1921. a fairly typical 13 foot wide baltimore rowhouse (that's baltimoreese for cheap townhouse)
There is no true subfloor, there is an existing tounge and groove 2 3/4" hardwood strip floor nailed directly to the joists and joist extenders. this floor is a little thicker than 3/4" and has been carpeted most of the time. the floor has been carpeted for 50 years i imagine.
Anyway, I pulled up the carpet and pad, and replaced the rotten and deteriorated sections with shimmed up 3/4 ply nailed to the joists.
The floor is uneven by 1/8" variance i would say (slight buckleing, wear, slight sag and old radiator holes) and also what appears to be tile grout or some kind of honeycomb patterned adhesive gunk on some strips (old bath location). these appear to have been sanded down enough so that 1/8 inch or so above the surface is the most uneveness.
is this an acceptable "subfloor" for what i am doing?
the flooring will be installed by a floor installer, not a full-blown contractor.
pictures to illustrate: