The structure was supported on a square set of twelve reinforced concrete columns, built over the Inner Ring road and the uncompleted bus interchange. The bus bays imposed a 36 ft pier spacing on the main block, and led to the standardization of a 1 ft 6in module for the design. Concrete was strongly expressed within the building, the external finishes to structural elements being unclad reinforced concrete. The walls were ribbed, and the locally graded round aggregate was exposed by abrasive blasting. The floors were made of precast concrete coffered units over which a reinforced concrete floor was cast. For the cladding Madin offered the council a choice of Portland Stone or Travertine Marble to align with the adjacent civic buildings. A third, cheaper option was pre-cast concrete with Hoptonwood limestone and Derbyshire spar aggregate with white cement: this was offered by Alan Maudsley, the City Architect, and accepted by the council as an economy measure.