The Curious Flaw of Amiens Cathedral

A few weeks ago, I was researching medieval church architecture for Book Two of my Hildegard of Bingen series (which will come out in February 2019). Part of the story concerns Hildegard’s project of building a church for her new foundation, which she wants to imitate the “French style,” i.e. the nascent Gothic style (though, of course, she would not know it under that name).

In the course of my research I found something surprising. I had always thought of medieval cathedrals as being feats of engineering, particularly impressive given the crude technologies available to architects and builders of the era. So many exquisite examples still stand and are in use after nearly a thousand years that I was quite surprised to find out that one church has a curious design flaw that had once threatened its very survival.

The Cathedral Basilica of Our Lady of Amiens, some 75 miles (120 km) north of Paris in the Somme River valley was completed in 1270 . It is the tallest complete cathedral in France (139 ft/42.3m). In order to achieve its height and accommodate large windows for more light, the cathedral’s external walls had to be propped by flying buttresses, an architectural invention that counteracts the lateral forces that push walls outwards due to the weight of the vaulted ceiling.

But to do their work properly the tops of the flying buttresses must be placed at a specific point along the wall, and in the case of the Amiens Cathedral that did not happen. The original builders placed the buttresses too high, and over time the excessive forces caused the arcs of the buttresses to buckle. The massive structure was in danger of collapsing.

Generations of churchgoers were lucky, but it was clear that that luck would one day run out. A first attempt to save the church took place in the late Middle Ages when a second row of buttresses was added underneath the original support. But that was not enough, and large cracks continued to develop in the arcade walls that would one day cause the pillars to collapse. To avert it, an iron girdle was installed to peg the columns in place and prevent them from being pushed outward. At the time of the installation, the iron chain was red hot, and it tightened as it cooled, acting as a cinch.

Design flaws were not the only challenge to the cathedral’s survival. There was heavy fighting around Amiens during both world wars, and during WWI the city suffered both German and Allied bombings. Thankfully the cathedral avoided serious damage, and in 1981 was added to the list of UNESCO World Heritage sites.

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If you are a lover of all things medieval, check out The Greenest Branch, my novel based on the life of Hildegard of Bingen, Germany’s first female physician. It is out now in ebook and paperback on Amazon US, Amazon UK, and several other Amazon marketplaces.