Visitors to I.M. Pei’s iconic East Building at the National Gallery of Art in Washington, D.C., have been met with an unexpected outdoor exhibit: A green construction fence surrounds the building as the museum prepares to remove and remount all 16,200 facade panels of pink Tennessee marble.

Museum officials are tight-lipped about the situation, and contractors involved are bound by strict nondisclosure agreements. But the National Gallery’s recent request to Congress for $40 million in repair funds called the problem a “systemic structural failure” originating in the anchors and clips that hold the marble panels in place. The project is expected to cost a total of $85 million and take about four years, the budget request stated, and the repairs “must be undertaken as soon as possible.”

The massive failure first became evident in 2005, when panels around an air intake shaft were seen to be tilting outward. The museum hired the engineering firm of Robert Silman Associates to investigate the problem. The engineers used probes to monitor the support system in places where the marble veneer had been removed.

The problem, Silman’s investigation concluded, stemmed from the facade’s initial installation. Completed in 1978, the building was clad in the same type of marble as the West Building, its 1941 neoclassical counterpart across Fourth Street, designed by John Russell Pope. But creating the East Building’s acutely angular shapes proved complicated. Whereas the older building is sheathed in nine-inch marble blocks, the East Building has three-inch-thick stone veneers set in large wall planes as long as 180 feet.

To handle the expansion and contraction caused by continuous temperature changes, the East Building has double-wall construction: Its marble veneers are held by stainless steel anchors and clips affixed to an inner masonry wall and to the building’s concrete frame. According to a 2008 monograph on Pei, this scheme was to give each marble panel the autonomy to expand and contract safely, separated by color-matched neoprene gaskets.

Silman’s team believes that the panels are tilting due to “locked-in” stresses arising from the “initial shrinkage of the concrete frame and the cyclical seasonal and daily thermal expansion and contraction of the marble panels,” according to a museum statement. I.M. Pei was not available to comment.

Temporary fixes have proved disappointing. Lead wedges inserted to stabilize the panels have transferred weight to surrounding panels at a risk of weakening them further. The stopgap efforts have failed “over very short timeframes,” which prompted the museum to erect the construction fence, protecting visitors from falling marble.

A version of this article appeared in AN 12_07.08.2009.