Soil stack - angled

[Paulboor]

I am remodeling an old farm house and wish to add an upstairs bathroom. I can extend the existing soil stack through the current first floor bathroom and hide it in a plumbing chase. But, at the top I run into the stairs leading the the second story. I would like to run the stack vertically and then follow the underside of the stairs at a fortyfive degree angle for about 3' of pipe. Is this allowed? If not, can I run the entire stack out of plumb to miss the stairs completely. How much out of plumb is allowed?

Also, do all first floor fixtures need to be vented now that I am connecting a second plumbing group to the stack on the second floor? They are currently stack vented.

Thanks very much for any advice.

Paul

 

[Slugbabydotcom]

You can run @ 45º or you can run a stack out of plumb so long as the 'neatness police' dont catch you.
I wont comment on the venting thing as I live in the UK and rules may be diffeent.

Suggest you post this on the US website