The Municipal Building's frame had of steel, which required 20 derricks to erect. The superstructure weighed a total of . The above-ground walls, and half of the beams in the superstructure, were carried by steel-plate girders at the first floor. The girders were connected to other steel beams, which distributed the building's entire weight to the caissons. Each of the first-floor girders were about deep and grouped in sets of two or three. The Municipal Building's largest girders, supporting the Chambers Street arch, were long and up to deep.