When I graduated three decades ago, there were serious concerns about the rapidly changing urban landscape as well as the lack of affordable housing and a growing social division. I observed experiments in alternative technologies closely, particularly those that promised environmentally friendly, cost-effective and socially beneficial constructional solutions appropriate to the context. My first acquaintance with ferrocement was in 1990 in Auroville, southern India. Twenty years earlier, the French architect Roger Anger had built a number of spectacular housing structures there using this material. They were the stimulus for further applications and resulted in this composite material being used later on a large scale in Auroville.
Today, the challenges are much greater. Modern architecture faces the task of having to reduce its use of resources, which makes an ongoing scientific examination of ferrocement worthwhile, since the many advantages of this material more than outweigh the disadvantage of its low thermal mass.
Homogeneous load distribution
In principle, ferrocement consists of a wire mesh reinforcement to which a roughly 25 mm layer of cement is applied on each side by hand or in a spray process. Although ferrocement consists of the same materials as reinforced concrete, it has a quite different load-bearing behaviour because of its lower mass. The steel mesh in ferrocement consists of a large number of fine reinforcing wires evenly distributed over the cross-section of a constructional element. The material created in this way is homogeneous and can resist both compression and tension loads. In contrast to concrete, no aggregate is added. The matrix consists only of cement, sand and water.
Plasticity and load-bearing behaviour
In view of the slender cross-sections of ferrocement components, they should be curved or folded to optimize their load-bearing strength. In contrast to reinforced concrete, this allows lightweight structures to be created with almost any desired curvature and with very small quantities of cement and steel. The development of the form thus plays a major role in the design process. Geometric optimization and technical know-how can lead to a maximum of built space with a minimum use of materials.
Although ferrocement was originally known for its application in shipbuilding, its plasticity and the need for a well designed form has attracted the interest of architects, too. Pier Luigi Nervi, for example, showed how well suited ferrocement was for roof structures (1). In 1948, the Italian engineer and architect used the material for the first time in an exhibition hall in Turin with a span of almost 100 m. To increase the speed of the lightweight construction process, he designed prefabricated roof elements. In 1971, the architect Roger Auger (see above) experimented in his first housing development, Auromodele, with free, flexible dwelling spaces that flow into each other. In contrast to Nervi's structures, Auger's double-curved roofs, with spans of up to 13 m, consisted entirely of ferrocement without any admixture of reinforced concrete.
Economical construction technology
In addition to a reduced use of materials, ferrocement offers numerous other advantages. In comparison with many other forms of construction, it is economical, and it contains less grey or embodied energy. The skills needed for ferrocement construction are simple to learn. Its diversity makes it suitable for hand-built structures, especially in developing countries (2). At the same time, it is well suited to industrial prefabrication and to forms that are cast in situ.
The low weight of such components reduces formwork costs. Ferrocement can, in fact, be designed completely without shuttering. Since the thin reinforcing wires are evenly distributed, the material possesses a great ductility and a high degree of resistance to seismic tension. What is more, it provides economical, simple and low-maintenance technical solutions that are water repellent and have a very long life.
Use in architecture: case studies
Continuing the series of experiments begun in Auroville, Anupama Kundoo Architects have used ferrocement in the following projects, later applying it in both developing and industrial countries, in labour- and material-intensive forms of construction, in hand-crafted buildings and in others, where high-tech equipment was used. The examples represent a holistic and sustainable approach that is relevant for developing countries in general and for India in particular.
Vertical fins: Pierre Tran Residence (1991)
Our first project was a 450 m2 housing development in Auroville, where the main consideration was to achieve a comfortable indoor climate. Vertical fins in ferrocement shade the facade of the building, serving to deflect light, to create diffused lighting internally, and to allow natural ventilation, which is essential in tropical, humid conditions. The two-storey building has self-supporting hollow terracotta roof elements in the form of vaulting and thick load-bearing brick cavity walls. The fins are detached from the walls and were cast in situ without formwork by constructing wire-mesh cages and plastering them from both sides.
Lost shuttering: Indian Pavilion (1999)
This circular hall-like structure 16 m in diameter was built primarily in reinforced concrete with two adjoining spaces each 55 m2 in area. Apart from these elements, there are no other walls dividing inside from outside. Tiers of seats extending outwards form a low-rise amphitheatre. A glass-covered opening in the middle of the roof allows daylight to enter here, emphasizing the function of the space as a central meeting point.
Reinforced cement concrete is known to be counterproductive in large-span structures where the dead weight is a problem. Several alternatives were designed in a bid to optimize the quantity of reinforced concrete used. The design that was finally selected required only 60 per cent of the concrete volume that would have been needed for other versions. The downstand beams are in the form of a catenary curve and are progressively reduced in depth. The beams and columns were cast in lost shuttering on the ground and hoisted into position manually before casting the slab. This provided an even finish and helped to reduce the cost of formwork.
Perforated facade: Wall House (2015)
The Wall House was designed with great openness as an inviting home. After 15 years, when it had to be extended, the proposed solution included a whole facade of ferrocement doors and screen elements. These provide security and privacy, while also allowing natural lighting and ventilation. It is an example of a low-cost, low-maintenance perforated facade appropriate to the climatic conditions.
Constructional unity: Children's Pavilion (2014)
A range of bent and folded geometries already tested in origami work to stiffen thin sheets of paper inspired the introduction of faceted forms of construction to shell structures designed as self-supporting roofs. The investigations led to ways of merging walls and roofs to form a structural unity. Finally, it was possible to translate curved shells into faceted surfaces that could be comprehended more simply geometrically and to construct them together with the necessary formwork. These forms require the use of considerably smaller quantities of material.
Modular construction system: Full Fill Elemental Homes (2014)
Full Fill Elemental Homes were conceived as an affordable housing solution that can be quickly implemented and provides modest spaces of high quality. The modular prefabricated ferrocement elements can be assembled on site in less than six days, including laying foundations. This flexible construction system allows residents to participate themselves; it also helps save furnishing costs: the thick container walls with open modules internally, provide ample storage space. The pigmented cement creates a colourful design in keeping with local aesthetics. Further surface treatment was not necessary. The production of the houses does not take place in a factory, but in the back yards of local builders. In this way, regional tradesmen are supported, workplaces are created and construction costs are kept low.
Outlook for the future
With a combination of theoretical research and hands-on full-scale experimentation on site, research into ferrocement as a building material is continuing with the aim of achieving further savings and greater efficiency. In this way, we wish to contribute to versatile, flexible housing construction, especially in those parts of the world that are undergoing rapid urbanization. In future, the main fields of research will be alternative forms of thermal insulation, corrosion-resistant reinforcement (using natural fibre mesh, for example) and the introduction of advanced types of cement.
