1The site proposed for the Rotch Library expansion was immediately adjacent to the existing library and the architecture and planning studios, in Building 7. While this was a desirable location within the Institute, close by the domed lobby at the Massachusetts Avenue entrance to the main building complex, the library site had significant dimensional and functional constraints. Earlier design efforts had not found a building solution that met these challenges while still providing enough space for the book collections.
2The library site was to occupy part of a building courtyard, which also served as the vehicle turnaround for one of MIT’s principal loading docks. Early in design, the project team studied the vehicle paths on the site and marked out the locations where the structure could touch the ground. Vehicles of various sizes demonstrated the feasibility of the structural layout.
3The space remaining for the building addition extended vertically from 14 feet above the ground to the cornice of Building 7. Spacing the new floors at eight and a half feet allowed us to fit six levels within the available height, with book shelving from floor to ceiling. Higher-ceilinged existing floors in Building 7 were programmed for reader services, study areas and library offices.
4The architectural proposal for the libraryset strict limits for the structural design: contain floor framing within seven inches of depth; avoid columns to grade except at the building perimeter; support book loads. The structural solution was to hang the six floors from paired beams at the roof, with inch-thick steel ribbons in tension as vertical structure fitted into the plan module of the book shelving.
5Constructing this system required first erecting the planes of structure along the addition’s edges, with temporary compression struts and tension cables, then hanging the steel ribbons from the roof, and finally forming the flat concrete slabs from bottom to top. In this photo: the four-foot-deep, paired roof beams and temporary zigzagging compression struts are visible at the top; the thin vertical line in the center is one of the steel support ribbons seen edge on; and diagonal cables penetrating the fifth floor formwork keep the structure stable until the concrete is poured. Only the cable sleeve locations, where the diagonal cables penetrate the forms, remain visible in the finished floors, as evidence of the building’s construction logic.
6Vertical fan-coil units, hidden at the ends of stack runs, eliminate the need for ductwork. This, and the structural system’s elimination of the requirement for beams, means that the approximately eight-and-a-half foot floor-to-floor height yields a ceiling height of eight feet. The addition consists almost entirely of book collections and vertical circulation. At the main point of connection to the existing building, however, a deep opening in the third-level floor slab creates a tall gallery space that draws readers into the addition and allows views of the main dome of the Institute beyond.
7The triple-glazed exterior wall of the addition maximizes daylight in the new bookstacks. The stack aisles, perpendicular to the long outside wall, allow the daylight to penetrate into the upper levels of Building 7, where an architectural studio desk retains a view through the addition.
8As with many MIT buildings, much of the library’s exterior architectural character derives from frank expression of structure. Aluminum cladding highlights the deep beams at the roof, thin slab edges float behind the glazed wall, and pairs of splayed columns mark new portals for trucks as they continue to circulate beneath the building.