Drain in behind cavity wall

We want to put in internal stairs and are moving a toilet into the main bathroom and moving laundry underneath the house to make way for the stairs (see floor plan). However there is a sub drain under the floor where the stairs will go. Seems as though we need to move this pipe hard up against the external wall, then have a stud wall hiding it. Problem is that we are really limited for space to fit stairs in and I only have about 200mm to house 100mm PVC pipe and a stud wall. Is this possible.. I have included a photo of what is underneath as well as stair dimensions. Any advice would be greatly appreciated on anything to do with this idea...stair dimensions anything that confirms we can do it.

Attached Thumbnails http://www.renovateforum.com/attachm...loor-plan1.jpg http://www.renovateforum.com/attachm...-sub-drain.jpg http://www.renovateforum.com/attachm...wall-final.jpg



Read the full thread at RenovateForum.com...