DETAIL spoke to Hermann Kaufmann about hybrid forms of construction, the ongoing development of the LCT system and its use in the Illwerke in Montafon and the building for the Wagnertec concern in Nüziders.
DETAIL: What do you understand by “hybrid forms of construction”?
Hermann Kaufmann: Hybrid forms of construction have always existed in architecture. Half-timbered buildings are a good example. The notion that the entire structure should be built of a single material is a concept of the Modern Movement. In former times, it was usually the result of a lack of available materials. In the context of historical urban developments, people commonly speak of “cities of stone”, but here, too, the floors were of timber. These examples from the past motivated us to consider whether everything had to be of wood, for example, even if one readily accepts timber construction. More important is to find as pragmatic an approach as possible.
DETAIL: Did the idea of the LifeCycle Tower (LCT) system, with its composite timber and concrete floors, come from this?
Hermann Kaufmann: Yes. The concept was developed from the need to determine what a particular form of construction has to accomplish – in this case, for an office building. Where vibration must be avoided in a structure with large spans, a timber and concrete composite form is a sensible solution. The additional weight is also an important factor in terms of sound insulation. The fact that the concrete elements, with their great weight, not only bear on the timber floor but support part of the load themselves, ultimately led to the hybrid floor element. This optimally combines the dimensions of wood and concrete components. Perhaps the term “hybrid form of construction” should be defined more precisely. First of all, there is the attempt to combine different materials in a single form; for example, where large spans are bridged with steel beams, and timber floors are laid on top. On the other hand, a composite element, such as a floor structure, can be created as a single entity – not unlike the combination of steel and concrete.
DETAIL: Different persons and institutions were involved In the development of the hybrid floor construction. Who was responsible for this overall?
Hermann Kaufmann: The hybrid floor system, using timber and concrete, was developed in collaboration with the Arup and Merz Kley Partner engineering offices as well as the Cree company, a subsidiary of Romberg Bau. The prototype for the floor element was produced by the timber construction firm WIHAG in conjunction with Goldbeck, who are manufacturers of precast concrete elements. The prototype was then subjected to laboratory tests in respect of its structural properties as well as its behaviour when exposed to fire.
DETAIL: You are a professor for design and timber construction in Munich. In researching the LCT system, wasn’t your architectural office involved as well?
Hermann Kaufmann: We naturally participate with the university in many research projects. But when it comes to developing realizable concepts, the most efficient way is via the office. The high level of experience and the knowledge of colleagues plays an important role in that respect.
DETAIL: After the LifeCycle Tower, you implemented the Illwerke Centre in the Montafon valley and the company building for Wagnertec in Nütziders (see page 1276), using the same construction system. Was this developed further in the process?
Hermann Kaufmann: It wasn’t a very great leap from the LifeCycle Tower to the Illwerke. We planned and developed the two projects at virtually the same time. Apart from the facades, the system was implemented on a one-to-one basis. The Wagnertec project involved an innovation, because we were not entirely satisfied with the production of the timber and concrete composite floors of previous projects. The problem lay in the many intermediate work stages involved. We wanted to simplify this and make it more flexible. So we took a closer look at the bolted connections. The method of construction by which the two materials are joined together on site and not at works offers considerable advantages: the erection process is simplified, the timber load-bearing structure is assembled by carpenters on site, and the precast concrete slabs, which are manufactured at works, are delivered and bolted into the structure afterwards. The timber beams and concrete slabs can be delivered in a more compact form if they are separate. We also wanted to create a composite system with joints that can be easily dismantled in the case of a future disassembly. The bolted connections allow the materials to be simply taken apart and disposed of. For Wagnertec, we incorporated an activation system into the components. The concrete serves as a thermal-storage material, and service installations are already incorporated in the slabs when they are delivered.
DETAIL: An unusual feature of Wagnertec is the brick external facing to the timber construction.
Hermann Kaufmann: That was a wish of the clients, and we happily accepted it. Most clients come to us because they want a timber building and wish to show this. Initially, we also thought of a prefabricated timber facade for this project. In terms of the constructional physics, a brick facade may seem somewhat strange, because one great advantage of brickwork lies in the thermal storage volume it provides; but in the case of a facing layer with a ventilated cavity to the rear, this thermal potential is not exploited. On the other hand, the material is extremely robust and durable. What the client wished to achieve with this was an expression of the basic values of the concern – things like hand-crafted quality and longevity.
DETAIL: What are the next stages in the development of the timber hybrid system?
Hermann Kaufmann: At the moment, we are investigating whether a timber and concrete composite form of construction could be achieved with an adhesive process. New and interesting products are available for this, like the strips that acquire their adhesive qualities by means of electrical charging. It would be possible to put the elements together and join them by charging the strip. If they ever had to be dismantled, the connection could be removed in a similar way.
DETAIL: Are you aware of comparable timber hybrid systems being developed elsewhere?
Hermann Kaufmann: Not at the moment. That’s probably because the development and implementation of such a construction system in our building economy – which is still organized on a very small-scale, compartmentalized basis – poses a great risk. The way the building sector is organized in Europe means that the market is not ready for systems of this kind yet.
DETAIL: Could it also possibly be because many architects feel themselves restricted in their design scope by a system of this kind?
Hermann Kaufmann: Yes, that certainly plays a role, too. Planners don’t have the same freedom as with other methods of construction. The form of the LCT was largely defined by the rectangular module, for example.
DETAIL: Does the new bolted connection allow a greater latitude in the design?
Hermann Kaufmann: Our aim is to make things much more flexible, whereby the use of separate components that are joined on site is an important step. We’re trying to exploit the scope offered by prefabrication to an optimum degree by connecting tailor-made computerized precast concrete elements with modern timber structures.
DETAIL: Why did you develop the timber hybrid system for office buildings and not for housing?
Hermann Kaufmann: Office construction is much more standardized and, therefore, more suited to a systematic approach. In housing, layouts and typologies are standardized, too, but the individual house or block is usually designed for a specific location. This tailor-made solution is at odds with systematization as we have developed it for office construction. What’s more, a local housing association usually builds with architects and firms from the area. It would only be possible to get your foot in the door if you offered a much more reasonable price.
DETAIL: Speaking of costs, can the office developments you’ve implemented with the LCT system be compared with conventional structures?
Hermann Kaufmann: Our construction system is, of course, not comparable with schemes in which composite thermal insulation systems and plastic windows are used. But in terms of higher quality standards, we are certainly competitive.
DETAIL: Does this form of construction also have a positive effect on the internal space?
Hermann Kaufmann: It offers great advantages. The wood acts as a load-bearing structure. At the same time, its material qualities can be experienced internally, where it has a positive effect on the atmosphere and indoor climate. More and more clients want to provide premium workplaces for their top employees. That was the case with the Illwerke Centre in Montafon, where we were also responsible for the interior design. The company sees itself as a regional energy concern and attaches great importance to value-added qualities in its area. A lot of the things that are commonly ordered from catalogues were implemented here by local craftsmen. This cannot be compared with what is common practice in office construction, where buildings are often erected very quickly to be leased out or sold off profitably.
