Materiality and surface Martin Peck
B 3.1
In the early days of concrete construction, there was a focus on using the material with new structural technology options and methods that were revolutionary at the time. Eventually though, builders also turned their attention to the finished concrete surface. An exposed con crete structure is characterised by the shape and texture of the form that holds the wet con crete, the formwork. As concrete construction methods developed further, new ways of designing surfaces also evolved. While exposed concrete construction initially concentrated on the material itself, there was an increasing focus on the surfaces that could be created. The appearance of an exposed concrete surface can vary depending on the kind of formwork skin and manual finish ing methods used. In time, the influence of various skilled manual building and treatment methods also became formative in creating exposed concrete surfaces. Such methods expanded the range of possible architectural variations, but also demand appropriate exper tise, control and construction experience. In Central Europe at least, exposed concrete is characterised by a smooth, flawless surface that has become a key trend in recent de cades. Although this trend seems to be contin uing unabated, there is now also a strong incli nation to explore other options. Heavy restric tions and the narrow range imposed on the material’s expressivity is increasingly giving way to a willingness to experiment and a desire for diversity and material authenticity in the appearance of surfaces. After a long phase as the dominant surface design, it will be some time however, before other forms are established as equally valuable alternatives. Surface design techniques B 3.1 Interior surface created using planed timber formwork with planks of various widths and visible nailing B 3.2 Interior surface created using planed timber formwork with visible light and dark effects due to the timber’s various absorption rates B 3.3 Church of St. Nicolas, Val d’Hérémence (CH) 1970, Walter Maria Förderer
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The techniques currently available for archi tects to create, control and vary the appear ance of a concrete surface allow design options as diverse as they are bewilderingly complex for architects. Older or what could be regarded as “yesterday’s” design tech niques, such as the use of timber formwork
or washed concrete techniques have faded from view and no longer seem to be present on the market. But after a phase of intensive development of concreting techniques and technologies, it would make sense to recon sider some older surface design techniques in the light of changed technical and technologi cal conditions and perhaps achieve entirely new results. Using the formwork skin in design
Now as then, the formwork skin usually determines concrete’s visible surface. Fresh fluid concrete hardens in the formwork and the surface of the structural element cre ated reproduces the inner surface of the formwork. Historic and current philosophies of surfaces Concrete surfaces were deliberately left visible for design reasons for the first time around 1900. The formwork and concreting tech niques of the time produced components with a very rough, uneven finish and rela tively strongly displaced surfaces bearing the imprint of the coarse texture of the small timber parts which made up the formwork, usually rough-sawn or planed planking. After about 1920, developments in concrete technology led to more reliable construction methods whose technical properties could be more easily controlled. This could not fail to have an impact on surface design. While the focus in the early years of exposed concrete was on the material itself, the appearance of concreted surfaces could be increasingly varied due to the different properties of formwork skins and the influence of construction operations. The use of coated plywood panels to manage large areas of formwork economically in the years after 1960 resulted in the creation of a new quality of very smooth concrete surfaces. A smooth exposed concrete surface with formwork joints and anchor holes is still the standard surface struc ture of this type. As smooth concrete became part of archi tectural language, architects increasing wanted (and contractors had to produce) flaw less surfaces.