AIUI, some years ago the regs were changed to require waste & soil pipes to be internal to the building, with which my house, built in the 70s, complies. This means that a 200mm square duct is lost from the kitchen and bathroom.
I notice that a neighbour, in order to get more useable kitchen space, has routed his externally, and I am wondering if I could do the same, if the need arises.
Is this a Building Regs issue?
Chris