Reno:
Regarding the boxes, plastic device boxes have a UL rating molded inside of the box, on the 'rear' wall. The rating is for wall and ceiling. That rating is for that particular box only, and in the 'tested' orientation. All of the details are within the UL White book, to be read with the patience of a saint.
Yes, there are many, many rated assemblies of walls and ceilings, bless the architects. The approved plans have the details for said assemblies, and that is how it should be fabricated. The designs are reviewed at plan review and must be built to plan, or have any modifications approved by the Arch/Engineer in writing.
Hopefully....the comments will pour in here!!!
