Formworks, First Impressions

Ruth Wang
Spring 2013

Fabric formwork for casting concrete is a field of research and experimentation that weds the solid and fluid states of the material, by showcasing the plasticity of concrete even in its solidified state. It is a method of casting, which utilizes a flexible membrane fastened, in tension, across a light weight frame- 

a concept originating in the Industrial Revolution. Yet, its parallels extend as far back as Roman Engineering. Pictured below are the impressions of reeds in Roman concrete vaults beneath the Villa Medici. Evidence of a process where retaining walls were cast in woven reed baskets.  (photo courtesy of Matthew Bronski)

The flexibility of fabric allows for a multitude of forms to emerge from a single form work, not only producing an exciting variety of forms and potential for experimentation, but also affording great efficiency and minimal waste in production. Pictured below is the P_wall by Andrew Kudless (2009), demonstrating the variety of intriguing organic, forms produced by a single type form work where the positioning of dowels is changed at every pour. 

Fabric formworks are also breathable, allowing for excess air and mix water to bleed through the formwork membrane, resulting in a smooth finish with minimal bubbles, blemishes and other undesired evidence of the mix and pour. 

While flexible, affordable, and efficient, fabric formwork has the disadvantage of being prone to inaccuracies. The inexact and flexible quality of the pour means the process of using a fabric formwork often does not require the use of advanced equipment, however, at the same time, the process is imprecise  Often, the only precisely controlled element of the process occurs at the locations where the formwork has been fixed to its supports.  Details of the Zero Waste formwork by Kenzo Unno and resulting wall in the URC house with grass in Edogawa-Ku, tokyo, Japan 2003, demonstrate the importance of the design, planning, and assembly of the fabric fixing points in the formwork. 

Another restriction of flexible membrane casting methods is that the design for the element to be cast must consist of convex surfaces exclusively. This is because the method relies on the principle that all textiles must be in tension caused by the viscous pressure of the poured material (concrete). Yet, this is also the beauty of fabric formworks as the final shape is the result of the intangible process that is the membrane's adaption to pressure.  These pressures can be manipulated so that evidence of this adaption can be revealed at different levels of resolution in the final cast piece. This is evidenced in a comparison of Miguel Fisac's Cultural Center (2000) and Madrid Rehabilitation Center (1969). 

The conventional way to produce unique cast elements is to manufacture one mold for each unique element- a process made more efficient and available by CNC milling. However, the conventional method is still very labor intensive, expansive and wasteful. Fabric formworks in combination with digital form-finding methods can achieve the accuracy of conventional casting, without the waste and inefficiencies. Employing flexible surfaces manipulated into a desired shape using a digital signal created directly from a CAD drawing of the design can be fast and automatic. Taking this approach, however,  may have limits in resolution, as it is best suited for large scale, double-curved surfaces, where the curvature of each panel or element is small compared to that of the whole surface. 

Digital form-finding methods such as the computational optimization method titled "Evolutionary Optimization of Fabric" (EOS) developed the Master’s thesis project of D. Veenendaal, Master student at the faculty of Civil Engineering and Geosciences of the Delft University of Technology (TU Delft), have been used to further refine fabric casting projects. 

Illa de Blanes in Blanes, Spain, designed by Arata Isozaki and Associates is a prime example. A seaside structure, featuring organically shaped columns, supporting a fluid roof form, the Illa de Blanes station was developed out of an evolutionary design processes based on EOS. 

Sources: 

http://www.umanitoba.ca/cast_building/research/fabric_formwork/
http://www.fabricforming.org/images/papers/G0304paper.pdf
http://concretely.blogspot.com/2013/03/lecture-prototyping-concrete-as.html
http://www.buildingcentre.co.uk/Prototyping%20Architecture.pdf
http://www.fabricforming.org/images/papers/Veenendaal,%20D.%20History%20and%20overview%20of%20fabric%20formwork.pdf