MASONRY VAULTS -
THE EAST AND CENTER WINGS

In his construction of the Treasury Building, Mills used only masonry vaults. Vaulted construction, using barrel and groin vaults, and sometimes domes, to distribute the weight of the ceiling and roof, is an ancient form of building, once used extensively by the Romans. The groin vaults that Mills used in the office spaces of the East and Center wings of the Treasury Department generated an efficient repetitive module that he could extend throughout the building that he constructed. These modular spaces lined either side of two barrel-vaulted corridors that intersected each other at a dramatic staircase.

Photograph of a groin vault - an intersection of two barrel vaults - at the intersection of the East and Center corridors on the second floor. The office spaces in the East and Center wings of the Treasury Building are the same.

The charge that Congress gave to Robert Mills, to construct a fireproof office building for the Treasury, determined the shape, feel, and size of the spaces on the interior of the two wings that he constructed. The spaces were dynamic, with the groin and barrel vaults clearly expressing the forces and tensions held at bay by the strength of the construction. Each space looked like the one next to it, but was distinct and separate compartmentalized by masonry walls supporting the weight of the building

This A floor plan of the 1817 Treasury Building, including the fireproof extension built by Benjamin Latrobe, drawn by Robert Mills in 1833, soon after it burned.

The very strength of the construction, however, was directly responsible for one problem with Mill's wings of the Treasury Building. Because each wall was an essential part of the structure, the spaces were inherently inflexible. To breach or remove any wall without adequate compensation compromised the structural integrity of the building. The repetitive module that worked so well, both as a design tool for Mills and as a means to make the building fireproof, was also the principal limitation of the building.

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