Toilet soil pipe - internal or external?

[cha21]

The soil pipe from my upstairs toilet runs internally, down through the room below.
I'd like to move it so that directly from the first floor it runs down the outside of my house instead.
Where can I find the building regulations relating to this. Is it allowed?

Thanks

 

[Hugh Jaleak]

http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADH_2002.pdf Check with Building Control, they'll need to be notified and likely will want to inspect the work.