Hoby Wagener and Thin Shells in Boulder

June 15, 2013.

First United Methodist Church

If you like to look at buildings, especially ones from the 1950s and 1960s, you may be familiar with what engineers and architects call thin shells.  As a rule the term applies to roofs-of concrete usually-that are much thinner that you think they would need to be.  The idea is that the shape of the roof, and some internal reinforcements, are what hold it up.  Originally conceived in the 1930s in Germany, they were popularized by the Spanish engineer Felix Candela in the late '40s and '50s.  

Casey Middle School

There are some examples in Boulder,  coming from one of our most prolific architects, Hobart Wagener. You have seen some of his more prominent projects, such as the Williams Village Residence Halls, Fairview High, the Kittredge Complex just north of Baseline, and the additions to the Boulder County Courthouse.

Fire Station #2

Wagener loved roofs and experimented with them all the time, so it is not surprising that he took an interest in thin shells early in his Boulder career.  I suspect that his interest may developed from a meeting with Milo Ketchum, who in 1953 did the engineering studies for trusses in a small Wagener-designed house built on Boggess Circle in Chautauqua Park.  





The most spectacular of these roofs was probably the series of four-gabled hyperbolic paraboloid bays over the addition to the First United Methodist Church at 13th and Spruce.  He used the same kind of roof, in concrete, on a personal residence, and wood versions for Boulder Fire Station #2, at Baseline and Broadway, as well as the side extensions on the Wesley Chapel, across Folsom from C.U.

Casey during demolition

Folded plates, in this case "Z" plates, were used to span the space across the cafeteria and gym at Casey Middle School; a distance of about 127 feet from front to back.  They are gone now, but photos taken during the demolition show how daring this design looks.

Community Plaza

For two commercial projects, Wagener chose to mimic thin shells; the roofs are built conventionally, but they look like they aren't.  Both are shopping centers on north Broadway at Alpine:  The Community Plaza Shopping Center, with what looks like a barrel roof, and the North Broadway Shopping Center, to the north, with what appear to be folded plates.

North Broadway Shopping Center

The curved roofs of the Community Plaza are actually T-beams, and the wooden roof of North Broadway are held up with conventional vertical supports and walls.

It seems to me that for Wagener, the roof was the starting point around which the rest of a building's design revolved.  While it provided a connection to the sky, it also could be used to organize the interior spaces, where life was lived.  His use of thin shells lasted only about a decade, but it played a useful role in the development of his architectural ideas.