Curtain Walls – Philosophy and Reality

by Don Friedman on July 20, 2016

The development of skeleton frames in the late nineteenth century made curtain walls – exterior walls of buildings that don’t carry structural load – theoretically possible. There was little precedent* for this type of wall and it attracted architectural theorists…a path that eventually led to the all-glass wall first as a theoretical concept and then later as a built reality.

Here’s a 1910s or 20s building on West 45th Street:


It’s one structural bay wide, so the only columns are in the side (east and west) walls. That means that the front facade could be all glass, and the first three floors approach that ideal. The upper floors have individual windows separated by terra cotta mullions; the big spandrel beams are also covered with tears cotta.

The terra cotta is not structurally honest. It’s fire- and water-proofing, but its form is that of ornament. The all-glass facade got its start, philosophically, as part of the International Style, and the gothicy facade here is far from that. And this building is where I separate from some purist theories: ornament is okay. I wish the design were better but I have no problem with the idea of it. The removal of structural function from the exterior wall allows the pure glass wall, but it also allows for terra cotta that vaguely resembles cake frosting.

* You can make an argument that the large windows in gothic churches were a form of curtain wall, but (a) they were not designed using engineering analysis and (b) their stability depends in part on gravity compression in their stone ribs.

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