The scarcity of wood for construction in Spain all but ruled out construction of beam ceilings or falsework for conventional vaults, and made it necessary to find alternatives. First applications of the material-saving vaulting technique appeared in Valencia in 1382, but the continued development of the Catalan vault took place primarily in Catalonia. Initially, they were predominantly employed to erect shallow vaults as ceiling decks; however, toward the end of the nineteenth century, particularly in the work of Antoni Gaudí (1852–1926), and his further development of the Catalan Gothic, new applications were introduced. His design for the Sagrada Familia (ill. 6) exemplifies the innovations in structural form finding and the evolution of the Catalan vaulting techniques. He employed the structural system, for example, in the colourful, ceramic-clad vaulted ceilings. In large industrial buildings, as for example in the Vapor Aymerich textile factory, erected in 1908, Lluís Muncunill (1868–1931) combined slender iron structures with multiple bays of vaulted brick roofs (ills. 2–4) lined up one next to the other. Further important developments and pioneering work was done by the Spanish architect Rafael Guastavino (1842–1908). In 1881, the specialist in industrial architecture emigrated to the United States, where he continued to develop and build the Catalan vault. After initial difficulties, he established a construction firm (later continued by his son) that realised nearly 1000 buildings in thirty states using Catalan vaulting. In New York and Boston alone, hundreds of banks, libraries, churches, and metro stations were covered with these roofs (ills. 5, 8). These vaults distinguished themselves through their impressive spans of up to 30 metres, and their brick surfaces visible from inside the building through their colourful ceramic-coated layer of bricks – often including ornate patterns. The Guastavinos made the Catalan vaulting technique amenable to mass production, and adapted it to the needs of the construction industry. In this manner, in addition to domes and vaults, numerous stairs were built (ill. 9). They recognized the competitive advantage of the fire-resistant structural system, tested their vaults extensively to prove their structural integrity, and developed or adapted innovations such as acoustic bricks or the use of Portland cement for the upper layers of bricks. Due to rising wages and the advent of new construction techniques that use steel and concrete, Guastavino vaulting was employed less and less for larger buildings. In comparison to new building materials such as reinforced concrete, brick was increasingly considered outdated and not suited to use in industrial structures. Modernism’s formal, rectilinear vocabulary drew attention to new possibilities for lean construction with steel, glass, and concrete. Nonetheless, there were some modernist proponents of brick. Le Corbusier’s design for Maison Jaoul (1956) was an attempt to use the Catalan vault in a modern building, but the application of this efficient and elegant structural system did not spark further realisations in the modernist vocabulary. In recent years, interest in the Catalan vaulting technique and its different applications has grown considerably, as well as scholarly research of it. The rejection of brick in favour of new building materials that took place years ago has now yielded to an awareness of issues revolving around sustainability and durability, particularly with respect to local availability of building materials and their eco-balance. The Pines Calyx conference centre in Dover convincingly demonstrates how local materials and Catalan brick vaults can be combined in an out-of-the-ordinary building whose embodied energy is 30% less than that of a comparable concrete structure (ill. 11).
Even back in Guastavino’s days, the labour-intensive construction process to build Catalan vaults constituted an economical problem, and it has been exacerbated by the increasing mechanisation of the construction methods. But in less industrial regions this apparent impediment can turn out to be advantageous. The brick, whose dimensions are related to the human body, and the simple form of construction provide the ideal parameters for the participation of local workers in the building process – a decisive advantage of the Catalan brick vaulting that was put to use in the Mapungubwe National Park Interpretation Centre in South Africa. One element of the building ensemble is a 3000 m2 exhibition space whose varying roofs have been realized with a series of domes and vaults (ill. 12). Local workers were included in the project, with great success, for the on-site production of the soil-pressed bricks and the construction of the vaults; this fostered an active knowledge transfer, and, at the same time, generated local jobs in the poorly developed region. The unfired bricks – with a cement content of about 8% to stabilise them – were pressed manually: this is an extremely energy-efficient means of production. SUDU, a research project that was carried out in a cooperative effort between the BLOCK Research Group at the ETH Zurich and the Ethiopian Institute of Architecture, Building Construction and City Development, also deals with the development of economically sustainable construction systems in regions with scarce natural resources (ill. 10). The concept of the prototypical brick masonry and rammed earth building is based on the availability of local materials and workers, but also on reducing the consumption of imported materials such as steel, concrete and wood. With total building costs for the housing unit of less than 60 Euros/m2, this construction method is ideally suited to poor regions in need of high-density dwellings. The aesthetic of the Catalan vault depends, on the one hand, on the material and brickwork pattern employed; on the other hand, it is determined by the building’s spatial quality and the vault’s geometry, which, because it is subject to compression forces, is defined in structural terms. The techniques to find the form for structures in a pure state of compression allow variations to a limited degree. In order to expand the constrained design spectrum, the BLOCK Research Group at the ETH Zurich focuses its research on the development of novel, three-dimensional form finding processes based on graphical methods. To this end, the freely available RhinoVAULT software provides the designer with an interactive environment to form find structures in compression. This design tool can be integrated in the planning process and aids the architect in developing suitable forms. With the help of this software, a Catalan free-form vault was designed, dimensioned, and realised as a 7.5 ≈ 5.5 m prototype at the ETH Zurich (ills. 13–18). The result shows that complexly shaped structures can stand efficiently in compression despite their free-form appearance. Aided by the new developments in form finding mentioned above, it is now also possible to locally incorporate tensile elements, such as a continuous tension tie around the free edge, to generate cantilevering forms that thus far have primarily been executed as concrete shells. A hybrid structure consisting of one layer of bricks, bonded to a thin layer of fibre-reinforced concrete, can meet the high structural demands of these novel funicular funnel forms (ill. X). The assembly combines the advantages of the Catalan brick vault – e.g. the minimisation of falsework – with the structural performance of modern building materials. The visible bottom face of the bricks is desirable both architecturally and structurally, and requires no surface treatment. The future possibilities to design exciting structures based on this elegant vaulting technique are legion.
