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While remodeling my bathroom and checking the floors for level, I noticed one corner of the bathroom had a 1/2" dip. I went to inspect the joists from underneath in the basement and found that a floor joist had been cut to make room for the toilet drain pipe. Hoping my terminology here is accurate. It looks like this repair consisted of installing 2 pieces of 2x8" with one end supported by the rim(?) of the house and the other attached to the adjacent uncut joist using a joist hanger (Simpson strong tie LUS26Z). The joist hangers were secured using drywall screws! One end of the 2x8s are lower than the supporting joist, where this must be the cause of my 1/2" dip.

My question is how do I go about remedying this issue? Ideally I'd sister the joist but the drain pipe is in the way. Aside from using drywall screws, is the repair sufficient?

I was thinking to remove the screws and replace them with these nails, doing the replacement one screw at a time. It's worth noting that the original joist has a crack towards the bottom edge of it where the hanger is attached. Should I be concerned about a nail causing the split to worsen?

I should add that the joists in my home are 2x10”, 16” on-center. The steel beam shown below is less than 3'-0" away from the 2x8s.

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    Is the 1/2" dip right over the joist end with the split in it? Is this dip away from a wall or toilet? What I wonder is if you could support the cut end, remove the screws, raise it up 1/2" then place the new screws, thereby eliminating the dip. What is the floor in bathroom? Experts here would have an opinion on whether it would cause damage to the flooring. Feb 22 at 12:45
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    I would prefer to use the Simpson joist hanger screws rather than nails simply because driving screws with an impact driver is much easier than swinging a hammer in tight quarters. The joist hanger screws will be thicker than a drywall screw, so they'll bite into fresh wood and should hold quite nicely. Make sure you get the 1-1/2" size, not the 2-1/2" ones. Also, that joist hanger is helping to hold the split joist together. Personally, I wouldn't be too worried about it, but others may have different views.
    – FreeMan
    Feb 22 at 13:07
  • The 1/2" dip is in the same location as the cut joist (which has a split in it). The dip slopes away from the toilet drain towards the exterior wall of the house. I'm in the middle of a bathroom remodel and haven't laid my flooring down yet - all I have is the subfloor above.
    – Niko
    Feb 22 at 13:10
  • You could support that joist, temporarily remove the joist hanger and use screws to pull the split together, then raise the joist so that the dip is eliminated and reinstall the hanger. You could even squirt some wood glue into the crack before you screw it. Don't put any split repair screws in the way of the subsequent joist hanger screws. This of course assumes that raising the cut end of that joist would eliminate the dip. Feb 22 at 19:10
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    I just read through the comments list, so I've deleted my initial response. All information should be in the question, not down here. Yes, your last comment sounds like what I would do. You don't need anything so extravagant as a bottle jack, though. Your car has one that will probably do just fine. Even a helper standing on a well-crafted lever has been known to work.
    – isherwood
    Feb 22 at 21:47

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No need to worry about sistering that joist. Since the headers are less than 3' away from that black, steel beam support, IRC R502.10 indicates that the single trimmer is adequate:

Single trimmer joists shall be used to carry a single header joist that is located within 3 feet (914 mm) of the trimmer joist bearing.

The low header is obviously the cause of your floor dip. It can be difficult to get them pushed up to the proper elevation, especially if you're a plumber. A post (a 2x4 would work) and some sort of jack (a car jack or even a wedge would work) will get it up to the top-of-joist elevation. The joist hanger toe-nails are going to be painful to remove (unless they are drywall screws too), but they need to get pulled back out of the trimmer to allow the header to move up to the correct elevation. Rather than remove the joist hangers from the trimmer, you can insert a wood spacer between bottom-of-hanger and each header if you prefer.

Don't worry about the split joist. It has 2 neighbors to make up for any strength loss from stuff like that.

Different Simpson hangers call for different nail schedules. Your LUS26Z calls for 4 - 0.148" x 3" face nails into the joist and for 4 - 0.148" x 3" toe nails through the header and the joist. Since you don't have a double trimmer for the 3" face nails, obviously you'll have to use 1-1/2" fasteners instead (Simpson makes 1-1/2" nails with the 0.148" diameter--that's a 10d common nail's diameter). The substitution will cost you 23% of the connection strength. Assuming your joists are 20 ft long or shorter, there will still be sufficient strength. You can find the nail schedule yourself by searching for "LUS26" within the full catalog linked from https://www.strongtie.com/resources/literature/wood-construction-connectors-catalog.

If you intend to substitute Simpson's screws for standard nails, #9 x 1-1/2" screws substitute for the face nails and #9 x 2-1/2" screws substitute for the toe nails.

And put some sort of electrical insulator between the bottom of that joist hanger and that copper pipe. And verify that all of those joist hangers have the same markings. One of them doesn't look the same as the others.

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