Moderator Post (s) for this thread: >Chicago Brickbydoug seibert on 07/25/2004
I agree with you, but there are so many variables we can't see from here. Joist replacement would be done from below by demolishing the ceiling. It may be possible to sister new joists along side existing, and tying into the top-sill (if not ballon frame) where the joists have rotted. The rotted components and affected floor section would have to be removed.
What kind of span are the joists?
Is your ceiling drywall or plaster?
Is the house conventional framed or balloon?
What would your contractor use to support the column and beam?
If the joists have failed allowing the floor to sag, how does supporting them on a beam and column provide a long-term solution?
Does his proposal include replacing the rotted section?
Sorry, more questions than answers, you probably need a second opinion (bid).