A prehistory to the Sussex gridshells

By chance or design Sussex is home to a remade structural form, the gridshell. Prior to the Sussex buildings, the gridshell's 20th century history demonstrates its unusual and singular past.

It is a sky blue summer open day at the Weald and Downland Museum, in Singleton, West Sussex. Crowds flock around the various traditional craft attractions, which, along with one of the largest collections in the country of renovated historical buildings, comprise the museums stock in trade. Up in the woods in the museums' southerly corner a sizeable contingent of visitors are clumped together, looking admiringly at the uncovered roof of the latest building at the centre. But this is no medieval, Elizabethan or Regency structure. It is a great weave of whirling timber laths, making three lattice-shaped shell domes, which will become the roof of this latest, only too contemporary addition to the museum. This is the Weald and Downland Museum's brand new gridshell building, which in the last year has won praise from press and public alike.

On this summer day the cladding has yet to be added. The structure looks like a beautiful ship's hull turned reverse side-up, but still naked as you can see the criss-crossing timber laths running in great long curves, some 30 metres, end to end. One year on from the open day the building has been completed, the cladding is in place, and after a big launch, the Downland gridshell is a stand-out showcase of what can be achieved with the emerging synergies of computer modelling power, related developments in glue and timber technologies, and a dedicated team of expert carpenters and sympathetic architects.

Beside the gridshell deck there is a viewing stand and standing on I, are representatives from its architects Edward Cullinan Architects, and engineers, Buro Happold. Together, project architect, Steve Johnson, and one of the projects engineers, Ollie Kelly, are describing to all comers exactly what they think they have been doing designing the building. At one of these packed talks an elderly man pipes up. He worked with Barnes Wallis during the war, and describes how Wallis applied the principle of lightweight wooden lattice design to hold the fabric skins of the Wellington bombers. Both Johnson and Kelly are visibly impressed.

Gridshells are lattice shell structures, shell-shapes pocked with diamond lozenge holes. Because the gridded shell form locks together, they are phenomenally strong, not requiring internal supports. Historically there have been a number comprised of steel, aluminum and concrete, the recent British Museum courtyard roof is a contemporary example of a steel version. Today, however a small number of all-wood gridshells have emerged around the country, within a few months of each other. Each is different representing a particular aspect of in the development of British shell structures. The Downland gridshell is the highest profile, amassing sheafs of press-cuttings, as well as being narrowly pipped at the post for the coveted annual Stirling Architecture Prize.

The history of timber gridshell engineering actually reaches considerably further back, to the early twentieth century. At the turn of the last century German and French engineers began putting onto paper nascent gridshell plans for agricultural buildings. From these early designs, adaptations appeared on World War I zeppelins, and in World War ll were developed by Wallis for the Wellington and other warplanes. But the real year zero for gridshell is 1975, when the pioneering German engineer, Frei Otto, completed the first genuine contemporary gridshell building in Mannheim. Originally a temporary horticultural exhibition hall, today this set piece of wood engineering futurism is a listed building. Subsequent developments in gridshell structures were primarily through those who were involved in the design, engineering and construction of the Mannheim building. A generation of engineers, primarily from Ove Arup – Otto’s Mannheim engineers– were exposed to Otto’s radical lightweight ‘minima’ building philosophy, first uncovered by observing the biological structure of double-curved coral, a textbook example of nature as a strategy for design. The entire Arup timber team, including Ted Happold, Michael Dickson, Ian Liddell, and Chris Williams would defect to form Buro Happold engineers, bringing back with them to Britain, their newly acquired timber expertise.

A related stream of confluence can be found in the work of Florian Beigel, who today heads up the Architectural Research Unit at North London University School of Architecture. Beigel, who moved to Britain in the early seventies, worked with the German engineer on his most renowned set pieces of engineering, the 1972 Munich Olympics steel cable stadium. He had already moved to Britain in 1970, and was also familiar with Otto's gridshell concepts. In 1974, working with his students, he constructed a series of four experimental gridshell structures on Highbury Fields. From there he tried to get funding support from Arup's and then Happold's to continue the research, just when the two big engineering companies were first beginning to research tension structures, but wasn't successful. The Highbury Fields' gridshells (documented in the Stuttgart Institute for Lightweight Structures Document IL13). Beigel, in a brief phone conversation, though not directly involved in gridshell design for a number of years, remains absorbed by its simple elegance to this day. Despite being double-curvature in form, he points out how the use of laths makes for a very simple element. Usually the use of the double-curvature form is difficult and the manufacturing expensive. "I still find the elegance of the idea very fascinating", Beigel says. For the first time, he notes, a way of using wood had been developed which enabled turning the square of the form into a parallelogram. Beigel finishes the conversation by recalling that his last direct involvement in the form was in 1992 when he was centrally involved in plans for a gridshell theatre and arts centre in Brentwood, Essex, It never got any further however, unfortunately. By this time, the mid nineties, the influence of the Mannheim building on the two respective Ted's, Cullinan and Happold, was already water long flowed under the bridge. Today, Beigel points out the Weald and Downland gridshell is exactly the same shape as the structures he and his students were playing around with on the playing fields near-on thirty years ago.

According to IL13, there were also two gridshell structures built in Japan in the 1980's, one out of timber, the other from bamboo. The first completed gridshell after Mannheim in the west was also emerged out of Japanese architectural culture. The country's submission to the Hannover 2000 Expo, highlighted collaboration between Otto and one of his most successful admirers, the Japanese architect Shigeru Ban was also a gridshell, similar in shape to Weald and Downland, but twice the size, constructed from cardboard tubes. But it was also a temporary and has since long been dismantled.

To significant extent the inspiration for the different gridshells, which have emerged during this millennium period can be traced to the influence of all Frei Otto's architectural and engineering colleagues settling in Britain. The summer of 2002, with the opening of Weald and Downland gridshell, became a quiet springboard, so to speak, for other buildings with unusually singular development in wood construction. The Weald and Downland gridshell stands as a geographic midpoint in a short triadic necklace of related buildings; Frei Otto's '90's Hooke Park Workshop to the west in Dorset, and to the east, the smaller adapted Flimwell Woodland Centre chestnut modular gridshell. Although the Hooke Park building is not a gridshell there are enough overlaps and similarities of philosophy that a persuasive interpretation can be advanced that the building is relates to this three-point cluster.

Both the Weald and Downland, and Flimwell structures provide something a testament to a new 'hands-on/hi tech' building paradigm; the convergence of developments in wood and related materials technology, and the new capacity for modelling which have been inaugurated by computers, and also incorporating the skills of the crafts tradition. Add to this the lightweight properties of the material, and a structural example of 'lightness' in design is apparent: a demonstration of how wood is one suitable candidate in the search for extra-light materials and structures.

As to the future, how will this putative gridshell movement look a dozen years down the line? There are signs that these buildings will be joined by further timber gridshells. Cambridge Botanical Gardens are considering an ambitious gridshell project, as are the Crown Estate near Windsor. In Chelmsford, a chestnut modular gridshell is on an architectural practices computers screens for a Park and Ride project. With a public tuned towards the curvatures of organic form, partially by way of a slew of grand millennium projects, plus a growing research and knowledge base, the next steps in a very specific strand of an architecture with organic form, using organic materials, is, at the beginning of the new century, in the early stages of multiplying. The Downland Gridshell has kickstarted an interest in the double-curvature rectilinear shell structures, and there is ongoing momentum as described above.

Below, the first two principle gridshell examples in this country are outlined and overviewed, albeit the latter is an adapted modular gridshell. Both were under construction at approximately the same time, the millennium years between 1998 and 2002. Both can be sourced back, either directly or implicitly, to the recent history and Otto's Mannheim building, and to a generation of, primarily but not exclusively Arups engineers. And both demonstrate a different aspect and slant on how the core structural conceit of a gridded shell can be applied as integrated roofing-building element in the ecological architecture of the early twenty first century.



Oak - the Downland Gridshell

Chestnut – the Weald Gridshell