The support box is intended for use when installing chimney in an A frame, in a mobile home or in a ceiling under a narrow section of roof. It provides a finished installation at the ceiling level and will support up to 20 feet of 6, 7 or 8 inch diameter chimney. The part also provides shielding from insulation when installed in an unoccupied attic space. The support box assembly is comprised of a black box designed for installation inside 16 inch O.C. joists, a cylindrical shield, support bucket, ceiling trim and four screws.