Abstract: An adjustable riser assembly for retrofitting an existing panel board enclosure with a replacement interior has a pair of base members secured to the rear wall of the enclosure with base flanges projecting forward. A floating member has end pieces with floating flanges that overlap and are joined to the base flanges by fasteners that engage selected ones of a second set of holes in each floating flange aligned along a first linear axis and a first set of holes in each base flange arranged in two rows each parallel to a second linear axis that is oblique to the first linear axis to adjust the height of the riser assembly. One or two planar members extending between the end pieces have a fourth set of holes that can be selectively aligned with a third set of holes in the end pieces for engagement by second fasteners to adjust the length of the riser assembly.