DIY’er here:
I have to run a 2nd floor toilet drain perpendicular to the floor joists (2×12). If I read the IRC correctly (using the code check flip book), the maximum hole size is 3 1/2″, which is exaclty the OD of 3″ schedule 40 ABS. How is it possible to get the drain pipe through the hole AND maintain pitch – since pitching the pipe would require a larger hole.
My old house had 2×10 floor joists & it had toilet drains going through the joists – don’t know how that passed since 2×10 only allow 3 1/8″ holes – then again, that house was 20 years old, so maybe the code is stricter on joist boring now?
Am I reading the code wrong or do I need to figure another way to run the drain? The room below is the laundry room, so I could possibly run the drain below the joists & box it in, but I’d rather not unless there’s no other way out.
Replies
Drill the holes so that they each have slight pitch, and so that the series of them has pitch as well. I have seen situations where plumbers had to insert 16" pieces of pipe with couplings between them, when there was no room to slide in a single piece from the end.
Do self-feed bits handle angles OK? Hole saws don't like it to much when one side grabs before the other - do you just hold on tight?
I already expect to insert a few short pieces.
Good right angle drill, and hold on. You can get an angled hole. Start slow.....
You dont need much as you will drop each hole 1/16" to 1/8" depending on your distance traveled.
3 1/2" hole is tight for 3" pvc, but is doable. 4" makes it nice, but you dont have that luxury in your case.....
Makes life A LOT easier if you can insert pipe straight on the hole, as oppose to angling up from above or below. You need bigger hole to angle and insert.
If possible, I drill in from exterior in a series of holes to slide the pipe in. Then go back and patch the exterior rim where the hole is. much easier on new construction before siding goes on....
good luck....
.. of course these can't just be drilled anywhere along the span of the joist, right???
How many joists do you have to bore? If you have to go too far, the slope requirements are going to put you outside of the middle third of the joist.
If you do bore, because of the limited access, you will have to do it in little pieces like David said. With all of the joints, you can probably get away with not angling the holes, just having them offset a little to get the slope you need.
SoulTrain ---
I don't know if you are reading the code correctly or not but ...
The hole size limits are based on the joists being loaded to their design limits. That is usually not the case.
If you are unable to fit your holes into the prescriptive code, perhaps an engineer can help you.
Thanks everyone, but I've decided to go ahead & run underneath the joists & box it in with soffit. Like I said, it's in the laundry room, so it's not a huge deal - I don't want to drill them & then be sol.