The building was constructed from wrought iron, with its walls and roof clad with corrugated iron. It has four storeys, with 14 bays on the main (north) frontage and 9 bays on the side return. The bays and floors are divided into regular units by high cast iron columns which support long cast iron beams with an I or H cross-section and supporting brackets, creating a rigid iron frame. Each unit on the north front has a full-width window with 5 casements (originally sashes), each with 3x2 panes, above a corrugated iron panel (replacing the original timber cladding, with brick infill added in 1946 on the ground floor). The west side has a gable end over the central 3 bays, above sliding doors on the ground, and hipped roofs on 3 three side bays. The south (rear) elevation is blind.
