We decided to insulate a 110 yr. old house, update electricity, etc. This house has drywall on top of lath and plaster and was insulated with stone and gravel. The floor is not level. The previous owners tried to solve the problem by jacking the beams in the basement and popped many floor boards. We noticed that cross beams have pulled up from the beams they were grooved into (or resting on). We thought the best way to fix the problem would be to strap the floor to make it level. It probably wouldn't be a good idea to take the jacks away (there has to be at least 15 of them).
Answer:
If you're going to all that trouble, why not install proper "I" beams and take out the majority of the posts. Now you can screw down the old sub-flooring and start from there with neither squeaks nor gaps. The cost too will be much more to your liking and you won't be left with yet another large cavity between layers of floor for vermin to occupy as an eventuality.
