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After construction, the original building was covered with an elastomeric coating for both concrete protection and to give it its eggshell white color.

Designing a repair plan
Since the Guggenheim's opening in 1959, the building has experienced cracking in the rotunda walls. Over the years there have been several attempts to repair the cracks and the building has seen multiple coatings of paint. Past repair attempts have failed, however, moving the museum's Board of Directors in 2005 to commit to a major restoration that would succeed in not only repairing the building but improving it so it could last for generations to come. "Every possible step has been taken to ensure this restoration has been done in a way that's faithful to Wright's design intent, but also faithful to modern developments and what we can do to create a better museum," says Brendan Connell, director and counsel for administration with the Guggenheim.

The undertaking includes renovation of the building's structure, updated windows and mechanicals within the building to help moderate a safe indoor environment for the artwork, repair of the Wright-designed sidewalks outside the building, and creation of an active maintenance program. The key to the renovation, as with most renovations of buildings of such high historical importance, is that nothing about the appearance of the building can be changed - all the repairs and updates will be unnoticeable to visitors.

The Guggenheim hired a renovation team of engineers, architects, materials conservator and contracting firm. The team knew it was under pressure to design the best renovation plan it could, not only because the Guggenheim is one of the most famous concrete buildings in the world but because there wasn't room, or money, for mistakes. "Generally speaking, when you start a project you do a conditions survey, you determine the needs, you select materials to do that, you write a specification, you look for qualified contractors, you ask them to bid, and then you find out how much it's going to cost," explains Norman Weiss, a professor of Concrete Technology at Columbia University and senior scientist with Integrated Conservation Resources (ICR), the materials conservator on the museum project. "Instead someone told us, 'Here's the price and get started.' So that was one of the challenges with this project."

Another challenge to the renovation team was it wanted to capture the as-built existing geometry of the building, both for drawings and a structural analysis model. This prompted a laser survey of the building. "The engineers used the drawing to do their structural analysis, and we used that analysis to make a set of drawings so we could look at cracking and materials lost," Weiss says. In addition, a survey of the building's reinforcement was performed using non-destructive testing, including ground penetrating radar.