The diversity of timber roof structures in the 19th century
In her dissertation, architect Kylie Russnaik analysed the roofs of railway buildings, riding halls and theatres in Switzerland. Her findings will help to better understand and preserve the wide-span timber structures.
The 19th century was an era of upheaval, driven by the steam locomotive and other technical innovations. This change also had an impact on architecture. “There was a great desire for innovation in the 19th century,” says Kylie Russnaik. “People broke with centuries-old building traditions and tried out new constructions.” The trained architect completed her doctoral thesis at Professor Stefan Holzer's chair, where she investigated the development of timber roof structures in Switzerland in the 19th century. During her research she discovered an astonishing variety of structural designs.
The thesis is part of the SNSF research project on the “Evolution of the wide-span timber roof in northern and central Switzerland 1600–1850”. In contrast to other buildings parts such as facades or interiors, that have often been subject to change in style and use, roofs are generally preserved in their original state with a visible construction and recognizable repairs. “Therefore they offer unique insights into the construction history of a building,” says Kylie Russnaik. In addition, wide-span roofs are particularly interesting because they were challenging to build and reflect the state of construction technology.
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Former military riding hall in Thun with construction detail -
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For 400 years, the rafter roof construction with the so-called “Liegender Stuhl” was used to cover larger spans. “The 19th century marked a time of transition and a shift away from this traditional construction method,” says Russnaik. Technological innovation gradually moved from church roofs to secular buildings. New building types emerged with large column-free halls and visible roof structures, for example for railway stations or riding halls. In addition, the emerging neoclassical architecture brought with it new forms, in particular shallower roof pitches, such as the wide-span semi-conical roofs of the newly emerging council chambers. The construction of the Mediterranean purlin roof proved to be better suited to these roof shapes.
In Switzerland - due to the absence of war damage - there is a unique stock of intact timber structures from the era, which had previously been little studied from a structural perspective. In her research, Kylie Russnaik systematically documented and analysed 54 buildings from Geneva to Herisau, identified the most important developments in construction technology and traced the evolution from traditional carpentry to modern timber engineering.
In contrast to churches, the studied secular buildings are often not well documented or published. “Identifying suitable objects was therefore time-consuming,” says Russnaik. The architect combed through military inventories, contacted cantonal heritage authorities and consulted the SBB. She examined the buildings on site, measured the load bearing structure with a 3D laser scanner and documented the joint details by hand. In her thesis, the doctoral student ordered the chapters according to building types and differentiated between assembly buildings, theatres, riding halls, railway sheds and functional buildings. “The function influences the construction,” says Russnaik. Riding halls do not require an attic, railway sheds must ensure ventilation, theatres require a lot of attic space for stage equipment.
Influence from Europe
As there were no academic training institutions for architects or engineers in Switzerland before ETH Zurich was founded in 1855, the trained carpenters or master builders continued their education in Germany or France. In this way, they brought new specialist knowledge from Europe to Switzerland. The German architect Friedrich Weinbrenner played an important role in the training of many of these architects. In addition, increased publications in building journals and carpentry treatises led to a faster spread of new building techniques.
Although newer materials such as iron or reinforced concrete emerged, wood remained a widely used material in Switzerland. In addition, the rapid technological progress in wood and iron processing led to a wide variety of new construction details. “I was surprised by the large variety of of constructions,” says Russnaik. In her research, she categorized the roofs in a chronological sequence, starting with the oldest constructions with a “Liegender Stuhl”, through Mediterranean purlin roofs to glulam trusses of the Hetzer patent at the beginning of the 20th century.
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Historical drawings of the Basel Central Station, which now stands in Bauma, as the photo shows. -
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From the mid-19th century, architects and engineers often combined the materials and used timber beams for the compressive loads and bending as well as wrought iron ties for the tensile forces. Such roof constructions were favoured because of their efficient assembly and low costs. The development of construction technology in the 19th century thus went hand in hand with a rationalization of materials, time and money. The profession shifted from traditional carpentry to technical principles that took into account the mechanical properties of the materials.
Many of the examined buildings are not open to the public. You can visit the former SCB railway sheds at Letziturm in Zurich or in Bauma, which originally stood at Basel Central Station. Most of the preserved halls are repurposed today, for example as storage halls or multi-purpose halls. Many of these important historical monuments are at risk. “Some of the buildings were even demolished during the research,” says Russnaik. With her work, the architect wants to draw attention to the buildings and raise awareness among experts. Her findings help to better understand construction practices and define criteria for preservation.
"Post-Traditional Carpentry: The development of wide-span roofs in 19th-century Switzerland north of the Alps", dissertation by Kylie Russnaik at the chair of Professor Stefan Holzer, ETH Research Collection