We are remodeling a second-floor bathroom. The floor dips, and my plan was to sister the joists to level the floor.
This is an old house, built in 1920. The previous owner redid the kitchen. The bathroom we are remodeling is above the kitchen.
I started pulling out the tub last weekend, allowing me to see into the floor and I noticed that the joists are already sistered , presumably to level the ceiling of the kitchen below. So I'm not sure whether I can even level the floor via sistering.
Should I get/cut narrower boards and rest them on top of the existing sisters or sister again on the other side of the joists? Or is there something entirely different I should do to level the floor?
Given questions in the comments about why there's such a severe dip, I am attaching a photo of a sistered joist under the kitchen floor showing a split joist, which I assume is the same reason the bathroom floor has a 1-2" dip.
Also, I tipped the old tub on its side, which allowed me to share pics of these joists: