Planning to move toilet... and found this.

[Brianr]

Toilet was plumbed through the center of a floor joist. They just cut out a section. OMG. I had planned to move the toilet laterally (now along the line of the floor joist) to accommodate a bigger vanity. However, when I ventured into the crawl space to plan for a new connection, I saw this. AND, it looks like from the second photo the sagging joist is resting on the PCV. FMR. Now what?!?!?

 

[JohnfrWhipple]

Time to fix it.

I would work from below doubling up the joist left and right. Block off the cut joist with some joist hangers from Simpson Strong Tie.

Support from below the joist if you can.

Get the structure repair so the new location works for you.

Any changes to your home's structure should be designed by a structural engineer. The end result will look something like this.

The illustration does not show joist hangers. Does not show doubled up floor joists but is close to what I would be doing.

This photo shows a good framing job for a sky light. The same techniques used below for a toilet.

 

[Sponsor]

 

[Brianr]

Thanks, John! I'd forgotten about blocking. However, installing the blocking could be problematic due to the sagging. I'm a PE, so I get the structural stuff. I think I'll put in some floor jacks to correct the sagging first, then block it out as needed. I may be able to use an offset flange in the new location.

 

[Terry]

I would jack the sagging joists up, and then properly block out. I would not not bother with an offset flange. They can cause issues.
I had one home that was low near the center by at least 2"
I used several jacks, poured a concrete pad, and supported the center beam. I had a lot of drywall repairs after that, once that section of the house was lifted. What you have looks to be pretty simple.