Eidlitz drawing of alterations to the arches in the Great Hall

In 1884 it was discovered that the Foundation Building required significant restructuring because of an insufficiency in its foundations and the piers that supported the fenestration of the first and second floors. This work was also partly due to vibrations from the American Bank Note Company’s presses on the fifth floor, and the fact that the structure of Petersen’s original building was experimental in nature. Architect Leopold Eidlitz was commissioned to complete this work.
On the first floor, every other pier on the 3rd and 4th Avenue sides of the building were replaced. Existing interior walls were also replaced, creating three arched hallways running north to south. On the second floor, the bands of small windows were replaced with larger arched windows and strengthened piers, creating a new look for the east and west façades.

As the original double height space spanning from the third floor to the ceiling of the fourth was deemed structurally inadequate, Eidlitz added four octagonal columns and structural girders to each floor to support the ceiling under the fifth floor. He also designed individual sleeves for each column and girder throughout the building, as well as new support girders running east to west to strengthen the weakened existing condition. Perhaps the most recognizable addition was that of two new diagonal trusses, which ran longitudinally through the building from the sixth floor to the basement.