How to cut hole larger than 1/3 of joist?

plumb_pete

I need to run a toilet drain (3”) through three joists (9 1/4”). Code states holes in joists can not exceed 1/3 the size of the joists. Catch is for 3” pipe I need a 3 5/8” hole — which is larger than 1/3 the height of the joist. Now what? I assume I could reinforce the joists, but I can’t find any specific info on this. Is there an approved way to handle this?

Originally asked by DA01 on Stack Exchange (diy) (CC BY-SA 4.0).

uphilltech

Great question — answering as the UphillTech team:

I have seen these before. I do not know if they are code approved, but it looks like a good start. This pic is from their website . It looks like they are not graduated lower to account for the fall of the pipe unless they oversized the hole to allow for some slope.

Full answer by Jack: https://diy.stackexchange.com/a/172031 (CC BY-SA 4.0).

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