Folded plate structures were invented in the 1920s and became all the rage in mid-century architecture around the world. They are capable of very long spans and have their own wonderful aesthetics, but they can be fussy and difficult to engineer and build. Take the new Southwest Library in Washington, D.C., dominated by its stunning folded plate roof made out of dowel-laminated timber. It is truly, as Heimsath described, a testament to the architect, Carl Knudson of Perkins&Will, and the engineer, Lucas Epp of StructureCraft in Abbotsford, British Columbia. And indeed, Epp tells Treehugger that he and Knudson “collaborated super closely throughout the project from the concept through to construction.” StructureCraft is the Engineer of Record for the project and did the engineer-build of the structure. Epp tells Treehugger there were numerous technical challenges and complications.