I own a 110 yr old row house that measures roughly 36'x20'.
7' from the Western wall is a beam (2 2x6's) that is load bearing to the 1st and I presume the 2nd and 3rd floors. Currently it is is supported by 2 vertical 6x6's and two jack posts. Otherwise, the joists run to the stone foundation that is in good shape.
The problem: The floor dips significantly to a low spot that is ~equidistant from the front and back of the house and ~9 feet from the western wall. The dip is very noticeable to me - 1 1/4" over 8'. The dip is only noticeable in the kitchen, as the 2nd and 3rd floors are ~level. The dip occurs directly over one of the jack posts.
The question: How do I go about leveling the kitchen floor?
I'm considering placing a 10-12' steel beam under the main beam and supporting it with the existing jack posts.
I am also considering adding a second beam on similar posts, ~8 feet from the eastern wall. What supports would I use? Would it need to run that beam the entire length of the house, or could I get away with just running it under the 10-12 feet that really needs support?
I'm decent with how to build new, but I completely lack the experience to know how to re-engineer safely and efficiently.