As diplomats from around the world gather this week at the United Nations headquarters in New York City for the annual General Assembly meeting, they are encountering a rare sight: scaffolding hung from buildings’ exteriors. After years of intense preparation, the 17-acre U.N. campus is undergoing its first major renovation since it was erected along the East River shortly after World War Two.

The sweeping renovation won’t come cheap, at $1.87 billion, with the cost to be split among all 192 member nations. But when it’s complete in 2015, the five-structure complex, whose 11-member design team included Le Corbusier, Oscar Niemeyer, and Wallace K. Harrison, may look more Modernist than it has for decades.

The well-known Secretariat Building, designed by Corbu and Niemeyer, will look especially different. “The building was a prince, it turned into a frog, and we have to turn it back into a prince again,” says architect John Gering, AIA, a managing partner with HLW International, the New York firm in charge of the lion’s share of project, which began in 2005.

By this summer, the 5,000 staff members who worked in the tower and the attached low-slung buildings had decamped for a handful of nearby high-rises. The offices in those buildings, which are styled to resemble the U.N.’s facilities, will be their homes for at least two years.

The U.N.’s highest-level officials, including the Secretary-General, meanwhile, have moved into offices in an onsite temporary building. The three-story, 230,000-square-foot structure, which was designed by HLW, opened on the complex’s north lawn in January. Its corrugated metal walls contain more than a dozen conference rooms.

Upgrading an Icon

While the Secretariat and Conference buildings, both completed in 1952, will be upgraded, the tower will receive a far more extensive gut makeover, primarily because of asbestos, which was found in floor tiles and around plumbing.

Plus, the goal is to give the Secretariat’s upper stories brighter, more open layouts— ceilings by windows will be raised while internal, non-structural walls on each of the building’s 40 floors will be removed. Indeed, 2,400 separate offices will dwindle to just 500, resulting in larger, more flexible spaces that can easily host impromptu meetings, says architect Michael Adlerstein, AIA, the U.N. assistant secretary who is overseeing the project.

Also, double-pane windows will replace the Secretariat’s single-layer versions to improve energy efficiency. In the process, the windows will lose their recognizable green tint, which comes from film added over the years to minimize glare, says architect Bob Heintges, FAIA, of R.A. Heintges & Associates, the New York firm in charge of replacing them. Syska Hennessy Group, a New York engineering and construction firm, will revamp the building’s mechanical systems.

To that end, both the Secretariat and Conference buildings will be made compliant with city codes, as they add sprinklers and wheelchair ramps, along with fire barriers inside mail chutes. Even though the U.N. isn’t required to meet these codes, as it technically sits on foreign soil, Secretary-General Ban Ki-moon insisted on it, particularly in regards to energy standards, Heintges says.

Original Details Preserved

While the U.N. campus will be notably updated, the renovation also aims to preserve much of its Eisenhower-era look. In some regards, the project will even bring the complex closer to its original appearance.

Retained will be Naugahyde furniture coverings and Formica countertops, says Adlerstein, adding that signs with period-specific Neutra typefaces that were removed decades ago will be replaced with facsimiles. In addition, much of the art donated by member nations, which lines the hallways of the Secretariat and Conference buildings, will be restored offsite and returned.

There will also be some mixing of antique and new: Ashtrays mounted on conference tables will be reconfigured for electronic devices, Adlerstein says, and similar versions by elevator banks will become vases.

“The U.N. has been very mission-oriented, and any money they got, they usually spent on food, peacekeeping, and disease,” he says. “Now, they are finally getting around to fixing their house.”

Restoring the Main Hall  

The project’s second phase, which will focus on the slope-roofed General Assembly building (1952), doesn’t start until 2013, when architecture firm Einhorn Yaffee Prescott will oversee a renovation that restores the soaring chamber’s wooden walls and adds new audio and video systems. Also a priority is repairing the roof’s small dome, whose copper-seam edges often leak.

Delegates from member nations who usually meet in the General Assembly will relocate to the temporary building, where a pair of adjacent conference rooms will be combined to accommodate the entire 1,000-seat body, Gering says.

Upgrading the U.N.’s complex, which has three times as many members as when it opened, is a pragmatic investment, says Stephen Schlesinger, the author of Act of Creation, a 2003 book about the institution’s birth. But it’s also a symbolic gesture, he says.

“It’s a very optimistic thing,” Schlesinger says. “It’s saying, ‘This is the way the world will be guided and shaped over the coming decades.’ ”