Possumblog

Obscure Architectural Term of the Day!

HYPERBOLIC PARABOLOID ROOF. A special form of double-curved shell, the geometry of which is generated by straight lines. This property makes it easy to construct. The shape consists of a continuous plane developing from a parabolic arch in one direction to a similar inverted parabola in the other. See figure 55.

From the Penguin Dictionary of Architecture, Third Edition.

Well, lemme tell you, if something needed a picture to go along with it, THIS is the thing that needs it.

Here’s a really cool Java toy from the one of the profs at the University of Minnesota that you can rotate with your mouse. (The paraboloid, not the professor.) And then there’s this site with all kinds of complicated words, and nifty paper things you can fold up!

This type of roof was most popular in the early Jet Age, mainly because it looks really cool and swoopy and modern and sciencey. Here’s an example, (more along the lines of a folded plate roof really, since it’s not curvy) of the roof of the National Library of Medicine in Bethesda, Maryland. They are structurally efficient, in that they can be formed by creating a very thin (like around 3 inches or less) concrete shell, with the shape giving it very high strength for its weight. But, you don’t see them much anymore (solid ones, at least--fabric dome structures still use the geometry to good effect). The Jetson’s look got to be passé, and they are rather difficult to manage during construction, and you can’t very well set a condensing unit on top of them or run vent stacks through them without ruining the lovely swoopiness, and they tend to wiggle around and make leaky spots where there are window frames underneath, and 3 inches of concrete provides a surprisingly poor thermal barrier.

Still, they are pretty neat to look at.

Posted by Terry Oglesby at June 2, 2005 01:29 PM