The building is constructed of Rawdon Hill millstone grit. As architectural master sculptors the Mawer Group produced the majority of the decorative carving. This did not include the rusticated and vermiculated base, the "giant" columns and fluted pilasters, the parapet with vases, or the basic detailing to the tower and ventilation turrets, which were the work of masons including Thomas Whiteley, who was associated with Robert Mawer. In preparation for the sculptural work, the carving areas were roughed out on the building blocks by the masons before the blocks were hoisted into place. The architectural sculptors would ascend ladders and scaffolds to carve the fine art pieces in public view.