I'm finishing my attic and have just realized that my rough carpenter screwed up by not addressing a cut joist. In photo 1, you can see that the joists have been sistered with LVLs, but there is a gap in one joist around the vent pipe (lower right). The small pieces of wood connecting the two sections of the original joist are resting on top of a wall below (perpendicular), but it is not a load bearing wall. In photo 2 you can see this area up close as well as the framing for a bathroom. The room has since been drywalled and tiled.
We were about to put the toilet in, when I realized I had better be sure that corner can take the 100+ pounds it will add. I am going to set the toilet box in the corner and see if I detect any deflection over the next month or so. (I'm putting joint compound along the top and bottom of the baseboards and will watch to see if cracks form.) If I see even the slightest movement I will ask my rough carpenter to come back and address the cut joist, which will mean breaking into the ceiling of the finished rooms below.
However, I'm not sure exactly what the fix should be. Maybe sister the two sides of the cut joist, except they do not align exactly. Maybe cut off each side and and put headers connecting the two pieces to the adjacent joists? Except that the adjacent joists should be doubled, and that will not be easy--the rooms below are finished. Maybe they can be strengthened with a steel place?