In the early 1970s, German architect Frei Otto and engineer Edmund Happold tackled an audacious challenge for the 1975 Federal Garden Show in Mannheim, Germany: creating a massive, fluidly organic hall without relying on heavy steel beams or concrete. The solution was the Mannheim Multihalle, an architectural marvel constructed using a double-curved timber grid shell. Instead of carving bent timber or custom-molding thousands of unique joints, the builders laid out a flat lattice grid directly on the ground.
Using simple hemlock pine laths connected at intersection points with loose bolts, the entire structure acted like a giant flexible mesh blanket. Workers then positioned scaffolding towers and hydraulic jacks underneath, gently lifting the flat grid upward to coax the wood into double-curved catenary arches. As the structure rose, the thin timber laths bent naturally along physical lines of force, guided by inverted hanging-chain models Frei Otto had spent years perfecting.
Once the desired shell geometry was achieved, the intersection bolts were fully tightened, and diagonal steel tie rods were installed to lock the flexible lattice into a rigid, self-supporting shell. Spanning over 9,500 square meters using laths measuring just 5 by 5 centimeters in cross-section, this temporary structure proved so resilient that it remains a protected historic landmark today, demonstrating the astonishing strength of lightweight grid shells.