Floor Joist and Roof Truss Oh My

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Scott Shepherd

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Hello everyone. Long time reader but this is my first post. I am an owner builder and am roughing in my plumbing on new construction. The house is single story with a crawl space. My area has not adopted a plumbing code (IPC or UPC), only the IBC.

I have a bathroom that is 6' x 9' that has (from right to left) a sink, a toilet, and shower along one 9' wall. I was planning to wet vent the group using a 2" vent from the sink but my plans were foiled when I discovered there is a doubled up 2 x 12 floor joist under the wall behind the sink & toilet so I cant drill down for the sink drain. To compound the problem further, there is a roof truss sitting on top of and running parallel with the wall behind the sink and toilet so I can't drill up either. A couple options I have thought to do-

A: Drill more or less diagonally through the sole plate behind the sink and in essence notch the top of the joist enough to get an 1 1/2" street 45 down through the wall past the joist and wye that drain into the 3" from the toilet. because I cant run a vent up from the sink because of the truss, I would use an air admittance valve for the vent on the sink. I would then run a 2" vent from the shower drain up into one of the other walls and wye the shower drain into the 3" line coming from the toilet. I am hesitant to do this because I don't want to accidentally cut too much out of the joist (more than 1 7/8") and I would rather not use a mechanical vent unless I have to. Also, I don't want to bring the vent up behind the sink above the flood rim and run it horizontal around the corner to the other wall and then up to the attic. The framing is 2 x 4 and I don't want to weaken the corner too much with boring holes.

Option B:
Put a 2" sink drain/vent in the wall on the right side of the sink where there is a stud bay with no joist under it or truss above. I could wet vent the whole group from there. I have never seen a sink drain exit the sink cabinet on the side, only in the back or through the floor below so this seems like an odd way to get the job done.

Hope this makes sense, anyone have any ideas? I am not concerned about how much material I use - I would rather have too many vents than not enough. Thanks.
 

Cacher_Chick

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Another option would be to build out the wet wall. It will take a few inches away from the width of your room, but should be one possible option.
 

Scott Shepherd

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Another option would be to build out the wet wall. It will take a few inches away from the width of your room, but should be one possible option.

Thanks for the post....I did consider that but being the sort of fellow that apparently doesn't plan things out very well, I have already installed the toilet flange. Building out a wet wall would require moving the flange and dealing with the hole I already made.
 

Reach4

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How about jogging around the big joist at 45 degrees. 45 degrees is considered vertical. Let that jog out of the wall be inside the lavatory cabinet, and thus hidden.
 
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