You need headers on either side of the destroyed joist to span the space between the hacked up one and a complete one.

If you choose to secure to the joist near the rim joist you will have to use hangers. A palm nailer may be useful in driving the fasteners.

If you choose to use headers in the other direction, you may have to double up smaller ones if there are obstructions in the way.

Another possibility is to scab together two lengths of 2x10, jam them between the far joist and the hacked one, then spike through all four pieces of 2 by.

(As you probably know, no notching at all is allowed in the middle third of a joist. I always wonder what these hacks think is holding up the house.)

This post was edited by worthy on Wed, Jul 31, 13 at 20:04

worthy: by "headers on either side" do you mean perpendicular blocking? Or sistered joists? Or to basically box out the joists around the hack? I'd have to go a decent distance from the hack to get a clear space to go perpendicular, as the drain line runs through the joist bay.

Not sure I can finagle 2x10s in between the rim joist and the hacked joist with all that plumbing in the way.

Oh, btw, this is another drain line a few feet to the right.

So no-go on the joist-to-CMU support?

What about those joist supports that brick eye has mentioned? I'll see if I can find them and repost, but maybe you can email him and send a picture and ask.

Will any of these work?
See link

Here is a link that might be useful: joist reinforcer

box out the joists around the hack

Yes that's it. If you can't do it within four feet of the hack, you should use two headers on either side.

Nice reinforcers! However, they're for limited size holes; your joist has been reduced to an inch or so.

This is a pretty standard thing that has to be done on virtually every new home; once the framers have finished, in come the HVAC guys with their chainsaws and the plumbers with their hole-saws and Sawzalls! Then back comes the framer to patch it all up again.

I'm liking those joist reinforcers, but it looks like I don't have enough wood left to attach them to.

Boxing out may work. I can go 4' away in either direction (total 8' long box) and still meet code?

Is the joist attached to CMU supporting the hacked joist not a viable option?

This is what is done for stairs openings.

Under the Code I work under, Ontario Building Code,

"9.23.9.5. Header Joists
(1) Header joists around floor openings shall be doubled when they exceed 1 200 mm [3.93 feet] in length."

As I suggested earlier, I think solid blocking between the hacked joist and the far one and then spiking it all together could be acceptable too. You might check with local building officials to be sure.

The damaged joist was never carrying much load and that might be some kind of cabinets above.

Worthy's solution is good if the plumbing is not in the way.

Can't you just put some blocking behind the damaged joist and TimberLOK through it to the rim joist? Or install a metal angle or PT blocking under it screwed into the edge of the plate or the wall? Or put vertical blocking from the sill plate to the top of the cut-out?

If the subflooring can span more than 16" o.c., the joist isn't necessary anyway. But without seeing it I can't say for sure.

Can't you just put some blocking behind the damaged joist and TimberLOK through it to the rim joist?

Theoretically yes, but I can't see a way to get any boards behind the hacked joist without removing more of the joist. Too tight/tangled.

Or install a metal angle or PT blocking under it screwed into the edge of the plate or the wall?

This was my original thought. No one was blessing it until now, so I wasn't sure it was kosher. Is PT ok in a crawl space? I know it's not in a basement.

Or put vertical blocking from the sill plate to the top of the cut-out?

Same issue as above with access.

Why would PT lumber not be allowed in a crawl space or a basement?

Offgassing.

is there space to put a concrete pier under the ends of the joist and posts?

HU-341610042, 8 years ago, hopefully @weedyacres has come up with the solution. Also possible they have moved on to another home as she still posts here quite often.