‘Laborious and difficult’: The evolution of Pier Luigi Nervi’s hangar roofs (1935–41)

Writing in 1938, Pier Luigi Nervi noted of his recently completed concrete aircraft hangars at Orvieto that “the reinforced concrete hangar can aspire to a true technical primacy, with minimal use of steel”. Completed in an era of shortages due to trade embargoes, Nervi’s hangars attracted global attention for their static efficiency and striking lamella patterns. But, while publicly sanguine about the hangar’s structural accomplishment, in private Nervi was frustrated with inefficiencies in their construction processes. “The actual construction was not easy,” he recalled in 1956. While the shells had minimized structural material, their complex shapes had required an enormous amount of timber formwork—also in short supply. Worse, the shells’ monolithic nature coupled with their extraordinary length led to nearly disastrous thermal expansion. In 1939, the Italian Air Force commissioned a second generation of hangars from Nervi, and for these he developed improvements that related to the structural form of the shells and to their fabrication. By prefabricating truss elements of the lamella grid, Nervi was able to save dead weight, which in turn allowed him to perch the new shells atop just six buttresses. The trusses’ light weight enabled them to be hoisted and placed with small cranes, and to be temporarily supported by a lighter, re-usable scaffold. The resulting hangars were able to absorb significant thermal stresses; they were light enough that they minimized reinforcing at their buttresses and were visually striking enough that Nervi commissioned Rome’s leading architectural photographer to document their web-like appearance before being covered. This paper examines the advances between the two generations of hangars, showing how construction inflected and refined Nervi’s static intuition.