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Apr 8th 2020

Technology and History Can Guide Architectural Restoration

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More than a year has passed since Parisians watched in horror and sadness as Notre Dame Cathedral, a symbol of national pride since its construction in the 12th Century, was partially destroyed by fire.

First, melted scaffolding needs to be removed from the charred and broken Notre Dame before any architectural restoration begins in earnest. The scaffolding was in place for a $6.8 million restoration that was nearly completed when the fire struck. A team leading the post-fire reconstruction effort intends to remove the scaffolding in March before beginning the painstakingly careful repair work out of fear the building’s vaults could collapse. The French government, which leads the team, wants to ensure every restored artifact aligns with tradition and the expectations of future generations.

Notre Dame Cathedral isn’t the first — and won’t be the last — historic building to be restored after falling into disrepair or being destroyed by natural disaster or war. French restorationists will undoubtedly make decisions that are informed by the spirit of the structure, but they also can seek guidance from the rebuilding of other acclaimed historic buildings and new technologies.

Starting Over Again and Again

Contemporary U.S. presidents don’t actually stay in the same White House that George Washington lived in when he was in office. For one, it was then called the President’s House, and — until John Adams’ presidency — it was in Philadelphia. But more exactly, the building that became the White House was lost to a fire set by British troops that stormed Washington, D.C., in 1814, two years into the War of 1812. Although it took 10 years to construct the first White House, its architect, James Hoban, returned to the wreckage to reconstruct a new one in less than three years.

Hoban was able to reuse stone walls, significantly hastening the rebuild, but he also saved time by altering the structural scheme of the building by using timber instead of brick, according to the White House Historical Association. Although resourceful and successfully working off memory, Hoban’s expediency led to a weaker structure that ultimately led to a demolition and rebuilding of the White House 130 years later.

White House reconstruction efforts pale in comparison with the many rebuilds of St. Paul’s Cathedral in London. The cathedral dates to 604 A.D., but it has had several incarnations after burning in several fires over the centuries. Viking raiders also destroyed it.

The Great Fire of London in 1666 claimed St. Paul’s yet again, leading a scientist, Christopher Wren, to lead an architectural restoration effort that illustrates the many demands on a project of public significance. After having designs rejected as too modest or too radical, Wren struck the perfect note with a plan to have the larger rebuilt church surrounded by dozens of smaller new churches. The beloved cathedral stood strong during the London Blitz, a German bombardment of the city in World War II, sustaining only minor damage and acting as a symbol of Britain’s resilience.

Bringing Notre Dame Back to Life

Modern technology now helps architects rebuild and preserve historic structures and determine how to create a restored artifact with the care and precision that restorationists and the public often expect.

Infrared thermography measures the radiation emitted by different materials to create a multi-layered look inside the walls of a building. This view can show preservationists where things are buried, whether a support beam has cracked and if anything lies beneath the surface. Ground-penetrating radar also helps detect structural defects in masonry and stone, and if any archeological remains are buried in the surrounding grounds.

Laser scanning could someday help bring Notre Dame Cathedral back to life. This process has emerged as a nearly fail-safe way to record the dimensions of structures should those many details be needed later. The digital photos can be used as “point clouds,” essentially detailed 3D models that can serve as blueprints for reconstructing buildings hurt by time, fire and natural disaster.

Because of the widespread affection for Notre Dame Cathedral, many recorded its internal workings before the 2019 fire. Vassar College professor Andrew Tallon led a 3D laser scan of the entire cathedral before his death in 2018. His continuous mapping of the church created a 3D image that Tallon said was accurate to within five millimeters and is considered a near-realistic image of the space that can guide the eventual reconstruction.

Of course, the materials used to build and repair Notre Dame over the centuries — including the timber that made the roof and the stone that shaped the vaults — isn’t readily available today. Still, Tallon’s scanned images will give the eventual saviors of Notre Dame a meticulous view of how the cathedral used to stand and how it can again stretch into the Paris sky.

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