I just completed my attached garage, which is attached by a one and a half story breezeway, and I want to plumb it out before finishing the 12x12 downstairs of the breezeway. I would like to have a full bath above the garage, but I don't know how to drain it. The floor joists are running the wrong way to get into the common wall to go down to the full basement. The floor joists are 2x10, but I think it's risky to bore even a 3" hole sloping through them. The breezeway has two floors and will be heated. The downstairs of the garage will not be heated. Is there any way to solve the problem without running the drain pipes under the floor joists rather than through them?
How do I run the drain from above the garage to the pipe in the basement? I have to run it about 15 feet horizontally before hitting the common wall with the house where I can run it down into the basement.