The firewall between townhouses in this area are commonly constructed of coreboard drywall set in "H" channel with resiliant firring screwed to it on both sides, some thin insulation, and 5/8" firecode drywall applied to that. There is no cavity for the boxes. So builders usually stretch the 12 ft. limit on the front and rear wall of the room or add a floor box. We are told "no penetrations" are to be made to the rated wall. Even the floor joists are run parallel to the wall without attachment to the rated wall.
