Prefabrication experiments - 104 - Ferrocement thin shell structures

Hybrid materials, their implementation, strength and versatility, exemplify the important advances of industrial development. The chemistry of plastics, the metallurgy of alloys aimed at improving steel or the union of steel and cement in reinforced concrete developed effective composite materials for construction. Modern architecture and its new programs benefitted from the large open spans engendered by the innovative use of these composites. Hardened cement reinforced with steel typifies the hybrid «modern» material. First employed as a kind of «magical powder» by Roman builders, the nineteenth century's production capacity directed a renaissance for hydrated and reinforced cement.

Patented in France in 1848, ferrocement preceded basic reinforced concrete by decades. Steel webbing encased in Portland cement produces a thinner, stronger and lighter material. As opposed to reinforced concrete, the cement is mixed without large aggregates and the steel reinforcing mesh is considerably tighter. The pasty mixture of sand, cement and water is troweled over compactly woven steel mesh or expanded metal lath: a fortifying fibre textile like surface. The monolithic hybrid's tensile strength and cracking endurance are superior to those of reinforced concrete. Produced in thin panels for finishes or for wall systems, the lightweight material also contributed to a revolution in structural capacity. Displayed most famously by Pier-Luigi Nervi in some of the most remarkable structures of the 20^th century, ferrocement embodied the idea of structural efficiency and material economy.

The concepts displayed by Nervi early in the 20^th century can also be found in the thin shell ferrocement prototype module proposed by the Leningrad Research Institute of Standardized and Experimental Design as a stand-alone house. The dwelling unit employed a thinly cast eggshell shaped ovoid structure. Weighing five tons with an inhabitable area of some thirty-five square meters the capsule could be airlifted or transported to any site. Its form resistant silhouette defined the thin shell’s sectional dimension of 120 mm.  Akin to fiberglass boat hull construction the composite cement and reinforcing mesh was completely self-sufficient and required no on-site foundations as the capsule could be deposited on  compressed gravel infrastructure. In matters of experimental prefabricated housing or temporary dwellings, Ferrocement is still put forward in developing countries as it requires little specialization and is merely contingent to the construction of a supporting mesh.

The ovoid shaped dwelling structure

 

Prefabrication experiments - 103 - Habitat New York II

Moshe Safdie’s Habitat 67 designed and built as an experimental prototype of collective housing for the 1967 World Fair in Montreal is certainly one of the most recognizable and distinctive architectural experiments of the 20th century. Renewing the modern tradition of demonstration architecture, it was at once a knowledge incubator and a catalyst for innovation. Proposed as the union of the single family dwelling with the benefits of shared infrastructure, the pyramid shaped utopia of grouped living shells or modules employed a rigorous geometric stacking informed by issues of proximity, circulation and dynamic architectural movement. Engaging a need for density, the experiment at the Man and His World exhibition in Montreal spawned from academic design research engendered multiple prototypes to be tested all over the world. 

One of Safdie’s many proposals explored geometry and modularity with a somewhat futuristic aesthetic. Somewhere between Japanese metabolism and Archigram’s hyper-dense living mega-structures, Habitat New York II was to be built in New York City's east harbour adjacent to the Brooklyn Bridge. The overall composition resembled Habitat 67's pyramidal shape but exhibited a more complex structural strategy. Slip-formed central cores or masts used for circulation anchored catenary structural cables encased in concrete, which produced the sail-like profile. The stacked modules were suspended from these stressed cables and occupied the space between the arc segments and the vertical piers. The octagon as opposed to rectangular prism was used as a basic building block combined in multiple organisations both in plan and in section.

Reintroducing on the era’s plug and play capsule aesthetic each unit's section related to its neighbouring unit. Flats were either one floor or split-level  «raumplan» configurations and the resulting dense interactions were offset by rational placement of both exterior spaces and openings onto magnificent views. The triangulated vertical clusters were placed on site in a diagonal grid pattern that maximized openness from the city to the harbour.

The somewhat artificial geometric aesthetic was a major change from the simplicity of Habitat 67. Habitat New York II was never built, due to lack of funding. It is part of a series of experiments that endeavoured to bridge the need to maximize social collective infrastructure with privacy and individual dwelling units. 

Habitat New York II - building section