Rebuilding Notre Dame (VIDEO)

At the Los Angeles Times, "Notre Dame may take decades to fix. The first concerns are water and soot":

Two holes gape where Notre Dame’s vaulted stone ceiling has collapsed. The cathedral’s 19th century timber spire is gone, as is most of its roof. Portions of the interior walls were blackened by the intense heat of Paris’ most consequential fire in centuries.

As the world absorbs the magnitude of devastation wrought by Notre Dame’s inferno, architects and engineers anticipate a decades-long restoration process replete with unprecedented challenges. Designers will need to navigate complicated structural issues and delicate preservation debates to satisfy an array of stakeholders.

They will all be asking the same question: How do you revive an 850-year-old icon?

"The whole world is watching, and everybody has something to say about it,” said Marc Walton, director of Center for Scientific Studies in the Arts at Northwestern University. “It has to be built for the next 1,000 years. It’s going to be a different structure as a result, but that’s not necessarily a bad thing.”

The first order of business is to dry the cathedral out, said John Fidler, who served as conservation director of English Heritage, a government agency that maintains England’s national monuments.

“There are millions of gallons of water poured into the structure that will seep down to the crypt, the basement,” Fidler said. Pumping out that water could take months, and years may pass before the entire building is completely dry.

“It’s easy to make the surface dry because there are large pores on the surface, but deeper in the stone, the pores grow narrower and it’s more difficult to suck that water out,” he said. “When the walls remain damp, you get mildew and mold and fungus and salt crystallization, which can rupture the pores in stone and cause it to deteriorate on the surface.”

Soot is also a particular concern because it’s so oily, said Rosa Lowinger, a conservator of buildings and sculpture based in Los Angeles.

“People’s first instinct is they want to wash it, but that’s the last thing you should do,” she said. The building’s limestone is porous, so soap and water would drive the soot into its pores. Instead, soot must be removed while dry. “The earliest decisions here — the protocols taken — will define how successful a project like this is.”

While conservators tackle those problems, other teams will get started on the greatest engineering challenge of the entire project: the assessment of the cathedral’s structural condition.

Most analysis methods are tailored toward modern buildings, not stone structures, so engineers may struggle to determine the stability of the damaged cathedral, said Matthew DeJong, a professor of civil and environmental engineering at UC Berkeley who has worked on historic buildings in Europe.

But Notre Dame is surely damaged, said Frank Escher, an architect and preservationist with Escher GuneWardena Architecture in Los Angeles.

“A fire of this nature can weaken a stone structure. It’s too early to say whether it’s safe or not,” said Escher, who is currently restoring the century-old Church of the Epiphany, the oldest Episcopal church in L.A...

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