Through an analysis of the work of Arjun Doshi, founder and Principal of the Pune-based Studio Acrobat, we explore the continuing fascination he has for Ferrocement as a building material as he attempts to establish a methodology and a technique for compelling structures.
The origin of Arjun Doshi’s strong interest in Ferrocement can be traced back to his childhood. Having spent a considerable amount of time on-site with his father, Girish Doshi and structural consultant, Vishnu Joshi (VD Joshi), Arjun had the opportunity to become acquainted with ferrocement construction in his early years. This is a memory that perhaps carried through. The latter, VD Joshi (who worked as a chief engineer with Joseph Allen Stein) was instrumental as a structural consultant in the making of Amdavad Ni Gufa (Hussain-Doshi Gufa), designed by Balkrishna Doshi. A collaborative piece of work between Indian contemporary architecture and art, the Gufa is a gestured narrative to the beginning of ferrocement construction technology in India. As a raw material, Ferrocement has contributed significantly in representing a striking array of contemporary Indian architecture built in the post-independent era.
Initially trained as a civil contractor, the impressions of these formative years led Arjun to become a self-trained architect by drawing inspiration from his interactions with Vishnu Joshi. Since the establishment of his practice in 2014, he has been experimenting with the material independently as well as collaborating on projects alongside other architects to build ferrocement structures of various scales. Today, he leads a team, all of whom are trained in various stages involved in the process of ferrocement construction generating originality and new sensibilities. With a comprehensive investigation of ferrocement as a structural material, Arjun has established a unique design methodology and process to execute the material effectively. His perspective is full of insights into the nature of the materials involved, the technique and the process. It is the process that he upholds as most significant in his opinion.
Essentially a derivative of a reinforced cement concrete system, ferrocement uses closely packed layers of a grid of smaller diameter steel reinforcement, sandwiched between three layers wire-mesh, and eventually encasing a layer of mortar on both sides of this structural wireframe. Ferrocement structures are constructed from the simplest of materials – cement, sand, water and mesh. These form the tangible components of the process. The material has an ability to enable complex curves, shells, vaults and free-form surfaces while challenging the conventional and more heavy alternatives. It demonstrates the possibility to generate differentiated planes in contrast to a static plan. Arjun fundamentally uses the functional aspects of the material repeatedly articulated in many new and experimental manifestation to from a fresh perspective each time. The crux of Arjun’s practice lies in the careful calibration of ingredients to set up a system under which the methodology to construct a ferrocement structure can be interpreted. The process is outlined hereafter.
INGREDIENTS
For the Cement Mortar Mix: Regular Portland Cement, Fine AggregateSand, Water and Admixtures, if any.
For the Steel Framework: A suitable reinforcement mesh (Chicken Mesh/Steel Mesh), Reinforcement bars.
TOOLS AND EQUIPMENT
Ferrocement has plasticity, gains texture, and can be completely made by hand with the help of only a few basic tools. There is no requirement of shuttering, concrete vibrators or even the concrete mixer. No special equipment other than a trowel and a wire mesh cutter is required to frame ferrocement structures. Other basic equipment required is the same as used for regular RCC structures and plastering. The tendency of the material to self-support large, homogenous surfaces impart ductility and is useful for larger spans as well. For instance, the meditation hall at the Triveni Ashram spans up to 48 meters with an average thickness of just 25mm of the raw ferrocement shell.
CONSTRUCTION PROCESS
A. Building The Framework
The close-spaced skeleton frame made with reinforcement bars is created in adherence to the geometry and shape of structure and is useful for retaining the wire meshes in exact location and form. The studio uses 8mm steel reinforcement bars that are spanned as per design. Every bar has a different angle to which it is bent separately then tied up in the grid. There is a series of these bars that form the complex shape of the shell. This defines the form and the geometry of the eventual structure. The weld mesh is placed on the reinforcement and wrapped within three layers of chicken-mesh. It is important to stretch the surface mesh so that it does not loosen up or warp in the process. The binding wire that holds the mesh together is woven around like a thread and cut to make it firm.
While concrete as a material is ideal for free-form structures, the skill to perfect the physical rigid formwork and shuttering is time- and labour-intensive. On the other hand, ferrocement allows for ample flexibility in cutting and jointing. During the construction of the Triveni Ashram roof, replicating the shell posed to be a challenge for Arjun’s team. The fine structural frame requires a measure of craftsmanship, in which site-work is mixed with shop-work, passing back and forth between site and the studio for necessary levels of precision. Minimising error and tolerance is a demanding task. The design of ferrocement structures require an interaction between the visual and the mathematical. A comprehensive understanding of construction of for Arjun was forged in this process, and it has since become a core to his practice. This engagement becomes refined over time with inputs from the construction workers and craftspeople on the site.
A statement from Studio Acrobat on the reinforcement and formwork reads: “The formation of ferrocement is TMT – 8/10/12mm. Weldmesh – 100mm X 100mm square, 2.5mm wire – 12 gauge. Chicken-mesh is 12mm wide (what you get regularly in the market is 25mm and does not work with ferrocement). Mortar is – Riversand, cement and water and not fine aggregate because fine aggregate makes it ferrocrete and not ferrocement, so ours is sand mortar only. Binding wire is 20-guage so it makes it easy to tie the knot, what you traditionally get in the market is 16/18 gauge which is used for RCC.”
B. Casting
Since ferrocement does not require formwork, the craft of scaffolding is very critical in the casting procedure. Ferrocement structures are conventionally produced by manually applying the cement mortar mix to the built framework. This mixture must be workable, but tested for excess-water for greater final strength and to ensure that it retains its form and position between application and hardening. The mortar is cast by troweling it through the voids thereof from one side and screeding the opposite side to achieve a smooth finish. This slurry is compacted by beating it with a trowel or a flat piece of timber. It is important that no reinforcement remains exposed on the surface.
This skill-based technique, if not executed with proper understanding, might result in cracks on the surface on the long run. Each stage of plastering is done without any interruption, and ideally in protected conditions. This stage is followed by curing for a minimum of fourteen days for the cement to achieve its maximum strength. The workability of ferrocement as a casting material needs both – an understanding of the structure and a skill level that is higher than the work of RCC and plaster.
Despite its structural solidity, ferrocement renders a certain quality to the built space. Arjun is aware of the visual qualities of his designs and he understands that the perceived weight of the structure depends critically on its thickness (perceptible at the edges). These forms stand out with their high visual impact and a seeming lightness. The washroom block of the Triveni Ashram is built of structural elements as thin as 30mm. The goal is to take advantage of the malleability of ferrocement to produce complex geometries that would otherwise require expensive shuttering and fabrication. Ferrocement structures, unlike the conventional building systems have the ease of flexibility and can be used in addition to many existing structures. Arjun’s first project, the Sangita Tapadia Office in Pune is an illustration of how ferrocement structures can be added on to existing structures. The design process involves typological analysis through a series of scaled models. Arjun’s practice innovates through a transformation of accepted interdisciplinary systems and by challenging spatial conventions. Working with scaled models and prototypes on site and testing them under the consultancy of the structural engineer, allows Arjun to manipulate the grids and make alterations where required. This method has proven to be efficient, both in terms of time and overall cost, and remains economically competitive when compared to regular construction systems.
A well-cast ferrocement structure survives decades (see the Gufa in Ahmedabad). The range of projects Arjun has executed make a compelling case that Ferrocement is not only used for small scale structures but also at a community level. The Loving Community Housing in Ahmedabad (Arjun Doshi in collaboration with SEALAB) features elements constructed in ferrocement. The project is an evidence of both – the economy of construction as well as the architectural finesse with which this material can be crafted.
Arjun Doshi’s works have set a graph of parallel explorations of ferrocement technology; which is an integral part of his approach to design. He has built his practice around ferrocement as a primary building material. As a material that is not often thought of as mainstream, Arjun has managed to make a case for the opposite. The spectrum of projects make ferrocement seem as a viable building material that is not just economic but also aligned with the aspirations of large spans, fine articulations and complex geometries. If used well, ferrocement has a potential to unlock formal, spatial and material potential of great architectural and structural value in a spectrum of possibilities⊗
STUDIO ACROBAT is a multidisciplinary design practice founded by Neha and Arjun Doshi; constantly experimenting with structure, material and detailing. They aim to create architecture that holds the place and people key, drawing expression from the context. A revival of age-old techiques of construction and finishing fused with contemporary design expressions in a significant part of their process. They believe committing to the process rather than the end product creates opportunities for the design for evolve. The two working teams of Studio Acrobat: Team A includes Amit Mhatre and Ramakant Thakur with 18 members from Pen. Team B includes Dilip Tupere and Rahul Ubale.
