The Art & Architecture Building, left, will reopen this summer with an addition, at right. (Chronicle photograph by Lawrence Biemiller)

New Haven, Conn. — Robert A.M. Stern and Charles Gwathmey, two of the most prominent and accomplished architects currently practicing, led hard-hat tours yesterday of a project that has consumed them both—-the renovation and expansion of Yale University’s 1963 Art & Architecture Building, designed by Paul Rudolph while he was Yale’s architecture dean and Mr. Stern and Mr. Gwathmey were among his students.

The effervescent Mr. Stern, who is now dean of architecture and who pressed the university to restore Rudolph’s iconic building, said it has been “a project with a thousand surprises”-—partly because Rudolph’s contract with the university had permitted him to make an unlimited number of changes, many of them undocumented, while the building was under construction. Most famously, perhaps, the eight-story building ended up with 37 levels, counting a multi-level terrace, stair landings for which Rudolph designed bench seats, and a penthouse with spectacular views of the Yale campus. The complexity of the renovation, along with Mr. Stern’s and Mr. Gwathmey’s insistence on living up to Rudolph’s high standards, accounts for its $126-million price tag.

Mr. Gwathmey once served as an assistant to Rudolph, and his firm-—Gwathmey Siegel & Associates Architects-—designed both the renovation and the 87,000-square-foot addition. As modest and reserved as Mr. Stern is outgoing, Mr. Gwathmey said the project had been a source of endless worry. He recalled attending a party at Mr. Stern’s loft right after the public unveiling of plans for the addition. Vincent Scully, the longtime Yale architecture-history professor, came up to him and said, “You should make the whole thing glass.” Moments later Peter Eisenman, the architect, told him, “You should let the limestone come to the ground.”

Mr. Gwathmey said he was so unnerved that he couldn’t eat dinner. He drove directly back to his office in New York and redesigned the facade, raising a prominent limestone element that echoes the window setback in Rudolph’s building. Then he had to talk Mr. Stern and Yale’s president, Richard C. Levin, into authorizing the change. “It was a moment of truth,” Mr. Gwathmey said.

The building the two architects showed off yesterday is structurally complete but is missing many interior finishes, including the orange carpet that Mr. Stern promises will match what Rudolph originally installed. The site was crowded with construction workers and materials, since the architecture and art-history programs hope to be moving in by early August. But the spectacular spaces and abundant daylight that Rudolph provided were easy to appreciate, especially in the two-story, open studio space that architecture students will occupy on the fourth and fifth floors. A similar two-story space on the second and third stories will once again house architecture exhibitions.

The renovation gives the building windows that are nearly as large as those Rudolph designed-—but that will do a much better job of helping to control temperatures inside, where Mr. Stern remembers students wearing mittens in the winter. The renovation also adds air conditioning for the first time, partly by installing high-tech ceiling tiles that will warm rooms in the winter and cool them in the summer. Mr. Stern said the project was expected to receive a silver rating from in the U.S. Green Building Council’s Leadership in Energy and Environmental Design program.

As the tours snaked from floor to floor and from Mr. Gwathmey’s addition to the Rudolph building and back, it was also easy to appreciate both Gwathmey and Siegel’s additions and its solutions to vexing problems. Mr. Gwathmey used the Rudolph building’s tower, he said, as a “fulcrum” between the old and new structures, and his facade uses limestone to echo Rudolph’s rough-ribbed concrete-—which was itself an effort to give concrete some of the qualities of stone, according to Mr. Stern said. Less-prominent exterior elements of the addition are sheathed in zinc.

The addition, which will house the art-history department, includes a number of spacious faculty offices, each with a view and each with a slightly different shape. Two new terraces, one at the top of the building and the other looking out just above the roof of the adjoining Yale Daily News building, will compensate for the complex’s not having a courtyard, as so many other buildings at Yale do. The addition located a new bank of elevators right beside the Rudolph building’s tower, where the two buildings connect through openings that were once windows.

The Gwathmey firm’s problem-solving deserves equal, if not higher, praise. The challenge of providing disabled users with access to Rudolph’s multiple levels, probably the most vexing problem of all, has been handled as gracefully as possible. Some of the sunken areas in Rudolph’s spaces have been given unobtrusive ramps, and in other places the sunken areas have been raised to the level of the surrounding floors. (The original floors and stairs have been preserved beneath, however.)

In addition, long-hidden skylights have been reopened, railings that were too low to meet current safety codes have been raised with new concrete, and new light fixtures will approximate what was in the building the day it opened. Mr. Gwathmey’s firm also significantly expanded the street-level library, which will serve all of Yale’s arts programs. Many of the features of Rudolph’s original library are preserved, including skylights, but a cafe will be added, along with space for more books and more students.

Mr. Stern said he had pledged that no class of architecture students would graduate without spending at least one full year in Rudolph’s building-—a pledge that limited the renovation to just over one year. Mr. Gwathmey, Mr. Stern, and the university decided not to try to erase marks left by earlier alterations that had cluttered the building with walls and dividers. The building will remain “filled with signals of its own history,” Mr. Stern said.

At the request of the lead donor-—the investor Sid R. Bass, who was a Yale undergraduate while the building was under construction-—the Art & Architecture Building will be renamed the Rudolph Building. The addition is called the Jeffrey Loria Center for the History of Art. The library that spans the two buildings will be called the Robert B. Hass Family Arts Library. The formal opening of the building is set for early November. —Lawrence Biemiller

A limestone element of the addition, at right, echoes the window setback of Rudolph’s original building. (Gwathmey Siegel image)

See a Tuesday post for additional photographs.