I am renovating an old house, and adding a new first floor bathroom. The issue is that i am very limited on soil pipe location. We have an open plan kitchen diner below and i dont want to change ceilings or have pipes running through that space.
The current idea is to run the soil pipe through a stairwell (leading from the kitchen to the basement) where i can box a spoil pipe in discretly. However the stairwell is not below the bathroom.
The idea is to combine all waste water pipes (vanity and tub) into the main soil pipe. Then running about 6-7' between the floor and below ceiling before dropping through the stairwell to the main house stack (easy once im in the unfinished basement). However the joists are only 3x8s and i know i cannot cut that much material out without causing code issues (not to mention structural issues). i know there are people out there who have reinforced with plates and brackets, and im wondering if people have an opinion on these? is it better to fabricate a custom steel plate and have an engineer sign off on that? Does anyone have a better solution?
I am happy to go down to a 3" soil pipe to aid the issue although if i can keep it at a 4" plate id prefer that.
your advice is truly apreciated. Thank you.