My builder warned me not to trim the poly film vapour barrier at the base of the studded walls. When I framed a new room in the basement I dutifly added a strip of poly under the bottom plate but now that I'm getting ready to dry wall, I'm not sure if that poly film goes up between the wall and the drywall sheets or between the drywall and the base boards. The builder gave me the impression that it was the latter but that doesn't make sense to me. Any advice?