This is a photo of the notched joist (on the left). It looks like they hardly have anything left of that section of the joist.
I'm going to have to figure out where the wall above there is so I can add a vent- currently there isn't one.
Meanwhile, it occurred to me that I was approaching the toilet venting the wrong way-- I kept thinking of wet venting or seeing if the north wall was less than 6' away so I could vent it at that point-- then I realized that I can run it to the closer interior wall and have the drain part merge with the horizontal part of the waste pipe for the lavatory. Instead of running the lav in to the exterior wall, I can bump the sink forward just a bit to give me some space to run the P-trap sideways instead of back.
I did run in to one main issue-- and that was figuring out the best way to reduce the toilet vent to 2". I tried to no avail to locate a tee that had the side and bottom at 3" but the top at 2" so I was thinking of using a reducing coupling after the top of the 3" tee.
Here is a revised sketch of the bathroom concept:
Here is is marked up with the lines to represent the plumbing (I suck at perspective so the stuff on the left side that is supposed to go in to the attic is screwy looking).
And here is my general concept of the parts to use and how they will be positioned. I didn't doublecheck it so I might have made some typos.
What do you think?
I'm debating whether or not to save pipe and space by just punching a hole in the exterior wall to put the vent for toilet and lav and routing it around the soffit-- but I don't like the idea of putting holes in exterior walls.