I have a 1920's home framed to minimum code with 2x8 floor joists 16"OC each spanning 12 ft. Our staircase up to the second floor runs along an exterior wall and parallel to the floor joists. Below the staircase are a second set of stairs leading down to the basement. The floor joist directly under the interior side of the staircase is only a single joist and over time it has sagged and deflected causing the stairs to tilt slightly away from the exterior wall about 1/8'' per foot. This has caused the treads to pull away from the stringer attached to the exterior wall. Any suggestions on how to fix this? Has anyone successfully jacked a leaning staircase back into position? My gut tells me in order to fix this I would have to meticulously take apart the staircase, pound the deflected floor joist back into position and sister in another joist along side it to beef up the structure and then put the stair case back together level and true. It all sounds very time consuming.