Reinforcing 3" drain line hole in 2x10

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Hi all,
Just started a master bath reno, down to the studs. The major plumbing change is relocating the toilet.

Existing toilet is plumbed as per the picture attached. It goes through the floor, makes a 90 turn through the 2x10, which is sistered with a 2x4 up top, about 8' long. Once in that stud bay it has a clear path to the drain stack. We are moving the toilet along that same joist bay to the other side of the room, so it will pick up the same vent stack, but I will need to recreate the reinforcement seen in the picture.

Some questions:
1) is the 2x4 glued and nailed still used in practice? The engineer in me (mechanical, not structural) tells me it should be fine near the end, as the proof is in the original design (~40 year old house).

2) should I up the reinforcement to a full 2x10? Or is that overkill? I can't run a full sister beam to beam without major tearout, but could easily scab in 4 feet around the hole.

3) I have access to a machine shop and scrap steel. I could mill out a 3.5" hole in a 9" x 24" plate and bolt it with 8 lags around the hole. Again, overkill?

Compared to this the other stuff on the remodel is easy (positioning lav drains, rerouting a couple of supplies).

Thanks,
Anthony
 

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Dana

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As long as the hole is more than 2" from either the top or bottom of the joist and the diameter of the hole is not bigger than 1/3 of the nominal joist depth ( 3-1/16" max diameter for a 2x10) it's pretty much good-to go without reinforcement. Read this.

If the hole is bigger than 3-1/16" (say 3.5") but still more than 2" from both the top & bottom of the joist it'll need something, but it doesn't have to be the whole length. A full depth (9.25") glued & screwed on CDX plywood gusset of 3/4" that extends a foot or so either side of the hole should be enough. It's easier to slip in a 2x4 or 2x3 than making a CDX gusset, go with that. A plate steel gusset would be complete overkill.
 
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Thanks for the info. I'm glad this is one joist and not a long run.

I'll make sure to get the hole exactly in the center. I only have 5' to the stack, so I should have plenty of room for drain slope in the joist space.
 
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