A Symptom Only

Another picture from Gabi’s visit to a church.

Those cracks look awful, but they are the equivalent of a fever: they are the response to a problem rather than the problem itself. In a true gothic-built church like this* the vertical buttresses, flying buttresses, piers, and arches make up a stone skeleton, and the walls between those elements are curtain walls similar to those in modern skeleton construction. That’s why buildings of this type can have huge stained-glass windows: the walls are barely structural.

That wall in the picture has cracked not because it’s overloaded, but because it’s been forced to move. In other words, the arch above it has deformed – maybe from foundation settlement, maybe from bad geometry in its design, maybe from unexpected load – and the wall has gone along for the ride. The pattern of cracking is useful to examine the movement of the arch, but that’s about it.

* As opposed to all of the fake gothic churches in New York that have exterior walls with gothic styling but no masonry vaulting below their truss roofs. St. Patrick’s cathedral, for example, has pinnacles on its outer buttresses, but no flying buttresses because there is no thrust to be contained.