Preservation and Modernism might seem to have contradictory goals, but not for architects Bruner/Cott. The Cambridge, Massachusetts'based firm is renovating and restoring Boston University's Law Tower and has just completed a 93,000-square-foot addition at its base. The half-century-old 18-story tower is a key element in a collection of five 1960s buildings designed by Josep Llu's Sert, the Corbusier-influenced architect and urban designer who fled to the United States from fascist Spain in the 1939. They occupy a site on the university's central campus between busy Commonwealth Avenue and the Charles River in Boston's Fenway-Kenmore section. In addition to the tower, the Brutalist concrete grouping includes two libraries, a student union, and a central boiler plant, making up what Bruner/Cott calls “a rare grouping of significant works by a single, internationally known architect.”

Although Moss and Cott—students of Sert when he was dean of Harvard's Graduate School of Design (1953 to 1969)—are ardent admirers of the tower's assertive aesthetic, its users have long criticized the building, which housed classrooms and offices, for its functional drawbacks. For instance, chronic traffic jams at its six small and slow elevators meant it would take students as much as 20 minutes to move between classes.

In addition, the building's envelope posed other challenges, primarily due to age and deferred maintenance: both its cast-in-place frame and its precast panels were spalling, exposing rebar, and its steel-framed, single-glazed windows were drafty and leak-prone. On top of that, the tower had been built without mechanical cooling (Sert's idea was that the narrow floor plate—only 60 feet wide by 120 feet long—would facilitate cross ventilation through clerestory windows and brightly colored metal panels). Although two separate air-conditioning systems were added in the 1970s and 1980s, both were outmoded and ineffective by the time Bruner/Cott was asked by the university to develop a preservation and development plan for this part of campus in 2007.

The tower was outdated in other ways—it had almost no space where students could gather to socialize or work in groups, making it out of step with the collaborative nature of 21st-century legal education.

Given all the tower's limitations, it is not surprising that the law school's leadership had long wanted to build a new facility on another site. Its dean, Maureen O'Rourke, says that the law school's relocation had been a consideration for at least the two decades that she has been a faculty member. Nevertheless, Bruner/Cott was able to convince the university and the school to move forward instead with a renovation and to build a glass and limestone-clad five-story addition, now known as the Sumner Redstone Building, over the one-story boiler plant. The scheme made compelling economic sense: the $184 million project (a sum that includes the expansion and the renovation, as well as soft costs like financing and design fees) is 40 percent less expensive than an entirely new facility, according to Gary Nicksa, the university's senior vice president for operations.

Cott says the project also makes sense for its users. He points to the project's “simple diagram,” which entails moving classrooms out of the upper reaches of the tower and placing them, along with new spaces for group study and socializing, in Redstone or on the lower levels of the Sert building. The tower's upper floors would be given over completely to administrative functions and faculty offices, where their occupants will enjoy views over Boston and Cambridge once the renovation is complete. The strategy is intended to reduce the crush at the elevators, and it locates the programmatic elements where structural logic dictates: the largest rooms are in the addition, which has a steel frame, and therefore longer spans, and the smaller spaces are within the tower's constrained waffle-slab floor plates.

One drawback to the approach is that Redstone's placement sacrifices some of the outdoor space that was part of Sert's composition. But Bruner/Cott maintains that the plazas were windswept and often in shadow, suggesting that Sert was applying a solution more appropriate to the climate of his native Barcelona than that of New England.

What the law school gets in exchange for the inhospitable outdoor spaces are indoor counterparts open to the whole university community. Expressed as glazed volumes that project from the smooth limestone skin of Redstone in a way that refers to Sert's cantilevers, the new gathering places include a caf' overlooking the river and a double-story winter garden that serves as an entry lobby. In the latter space, old and new are clearly distinguished from each other: muscular concrete stands out against a relatively delicate curtain wall. The contrast is reinforced by details such as the 10-inch-wide reveal where the winter garden's ceiling meets Sert's tower (the gap also hides an expansion joint).

As part of the tower's restoration, which is now in full swing, the single-glazed steel windows are being replaced with double-glazed versions in thermally broken aluminum. The new windows' mullions and transoms will match the profile and rhythm of the originals and re-create their shadows.

One particularly tricky aspect of the project is the repair of the spalling concrete, especially that of its cast-in-place structure, says Moss, since the appearance of the material is different in different parts of the tower. What's more, contractors must wait three to four weeks for samples to cure to see how well they match the existing surfaces. “Patching stone is a piece of cake by comparison,” he says.

The renovation also includes the removal of all partitions and the installation of completely new building systems, such as active chilled beams in perimeter offices, which will cool efficiently but work within the structure's tight floor-to-floor heights. Cott says that he hopes the project will redeem the tower in the eyes of the Law School's faculty and students. Once the restoration is completed in the fall of 2015, he says, “it will be better than it has ever been.”