Free-form with a Swiss accent

Switzerland's avant-timber manufacturer's Blumer Lehmann have developed an enviable portfolio of adventurous and 'free-form' buildings and projects. This, though, is only part of a broader operation, as a visit to their main Gossau base revealed.

Two years ago, through 2019, the Swiss timber engineering company Blumer Lehmann completed a wave of projects that underlined how over the last decade they’ve become one of Europe’s leading engineers in the niche world of highly complex digitally designed ‘free-form’ timber buildings.

The Urbach experimental tower, left, and right the
new Learning Centre at their breakthrough Haesley
Nine Bridges, Korea project - Urbach photo ICD/ITKE

In September that year, Blumer Lehmann handed over Shigeru Ban’s Swatch HQ and museum project - in their own watchmakers’ country, the French-German borderline town of Biel-Bienne. In Britain, earlier in the summer, they had completed the inner column trees’ calligraphy-like scaffolding of the world’s first green mosque in Cambridge, the first of two UK projects. A few months later, their work on the latest Maggie’s cancer care centre in Leeds was handed over. In Stavanger, Norway, timber pioneers Helen & Hard saw their largest timber project to date, Finanzpark, open – see this Annular Unstructured for features on all three projects. Far away, in South Korea, a set of phase two buildings were added at the timber-manufacturer’s breakthrough Haesley Nine Bridges Golf centre project. And to round off a significant year in their calendar the Urbach Tower a relatively short distance from their northern Swiss base, Gossau, in neighbouring German Baden Württemburg, opened.

Though there have been others since, notably the Magician’s Hat at Knie’s Kinderzoo on the southern edge of Lake Zurich, nothing in 2020 or 2021 quite marks out the reach of Blumer-Lehmann’s work in comparable fashion. As such Blumer Lehmann are part of a small group – you can count them on a single hand – of Swiss companies, known across the continent for their abilities to deliver ambitious engineering, design and large-scale projects in comparative straight-forward fashion. There are other Swiss timber operations, Erne, Renggli and Häring for instance, but it is only Blumer-Lehmann who can point to such a striking portfolio of free-form buildings.

Some of this is due to their one-time partner, timber engineer Hermann Blumer – profiled in the accompanying feature – and his ground-breaking timber engineering work. When Shigeru Ban was stalled on his Metz Pompidou Centre timber deck, with his original engineers Arup unable to realise a satisfactory system, he was on the edge of abandoning the design before being introduced to Blumer. Sent away to resolve the engineering problems, Blumer came up with a solution which unlocked the project. Blumer has been Ban’s timber engineer ever since. Some of this has to with the dynamic 21st century timber culture that has emerged over the last quarter of a century across ‘the Alpine and sub-Alpine regions of the pan-DACH countries. What Helen & Hard’s Reinhard Kropf, among others, has described as the ‘silicon valley of timber’ has provided an expanded smorgasbord of experiment, innovation and new thinking which has propelled the return of timber across the continent. A further oft-quoted influence is, given that the country lies outside the EU, are how the Swiss building standards and codes encourage, rather than discourage, timber engineering experimentation. I heard was told that this difference acts as a significant advantage: responsibility lies with the engineer, and if the engineer is up for taking the risk and the responsibility, you can do what you want within the regulatory framework. If this also means that Swiss timber materials need to jump through further Eurocode certification hoops, the kinds of risks and experimentation taken in Switzerland outstrip its EU neighbours. It has meant that those who are drawn to experiment – Hermann Blumer is the obvious case in point – are more likely to do so. And then finally, there’s the Swiss tradition for technical prowess, craftsmanship and skills, which can be traced back to the watch making tradition.

Blumer Lehmann's Erlenhof base, in the process of being expanded
Katharina Lehmann

In September 2019 I took a train from Zurich north-east towards Lake Konstanz with an appointment to visit the source of this free-form timber. I was met at Gossau Station by Katharina Lehmann, the CEO of the Lehmann Group. Blumer Lehmann is one of three companies sitting under the Lehmann Group umbrella, after a merger with Blumer's company. Since 2000 Blumer has not been directly involved, though the name remains.

Soon we were driving out of Gossau, turning off into a lane near the village of Erlenhof, which looked as if it led to a farm, when almost out of nowhere we are in the timber factory forecourt, steam and smoke pouring out as the rain starts to spit. In the car Lehmann had begun to relate a brief overview of the family company. She was thrown into the family business when her father suddenly became seriously ill, suffering a stroke in 1996. I make the mistake of asking what it was like to take over a business after her father, Leonhard Lehmann, passed away. "He's still alive but can't communicate," she says, matter-of-factly. She took over in her mid-twenties after finishing an economics degree. A brother also works in the company.

The Erlenhof yard

The company has been in existence for 146 years, since 1875, and began, like many other Swiss timber manufacturers, as a sawmill. Today there are 370 employees, with 200 involved in the actual timber constructions, roughly divided three ways: engineering project management and planning, production, and erection. Like so many of this current generation pushing the timber envelope, Lehmann’s father was a carpenter, who began building farmhouses and their traditional roofs between 1950 and 1970. This was the first direct involvement of the company in building.

Just at the time Lehmann took over from her father, construction was changing, she says, due to the impact of pre-fabrication. It broadened the repertoire of timber engineering possibilities. In 1997, Lehmann senior took over Hermann Blumer’s timber manufacturing firm, with the name updated to Blumer Lehmann. Blumer, she says, had his own view of timber. “It was in a way, traditional, but his version of tradition. He was pushing the limits, always.”

The Haesley Nine Bridges deck under construction

The turn of the millennium saw the spread of digitisation across timber engineering. For Lehmann as much as Blumer the advent of timber going into digital 3D planning kept things interesting. Digital tech introduced the prospect of greater control over the construction process. Projects remained overwhelmingly Swiss-focused, though it was Blumer Lehmann who built the restaurant for the Swiss Pavilion at Germany’s millennium Man-Nature-Technology Expo 2000 in Hannover. The century’s first decade was a period of developing their familiarity and expertise across a spread of comparatively new fields: “building physics, technical installation, organisational processes, all of these sorts of issues”

I ask Lehmann about the beginnings of the ‘free-form’ strand of their work. By now we have been joined by Kai Strehlke, an ex-Herzog de Meuron German architect, with overall responsibility for the CAD/CAM programming and production of free-form projects. It was Blumer’s link in with Ban, and particularly the Haesley Nine Bridges Yeoju Golf Club project in South Korea, that was to be the turning point in ushering in the new ‘free-form’ chapter.

In preparation - Glulam beams for Swatch

Blumer was the first to know. “I’ve got another project for you,” Shigeru Ban is reputed to have said down the phone after calling the engineer. What sort of project, and where, only gradually became clear to Lehmann: “The Haesley Nine Bridges project was the initial one to get into contact with programming and machining complex structures. Before that the words ‘free-form’ were never used. Shigeru Ban created a unique timber construction which forced and challenged us to push the limits in technology, new planning and building processes.”

Timber trees at Haesley Bridge - Shigeru Ban Architects

“When it came,’ Lehmann continued, ‘we had the courage. We knew it was a huge risk and we didn’t know if it would work. It was such a large risk, and we couldn’t have done it without the sawmill. It was clear that we did our part. But it wouldn’t have been possible without the other partners. We had to manage and organise a network, which was new for us, trusting each other, depending on each other.” It could have been much more difficult if they’d been working elsewhere, outside of Switzerland. Strehlke: It’s such high conflict, and lack of trust in construction in Germany. There’s a much higher degree of trust here, and you need trust.”

At the time they only had some of the technology resulting in capacity for prefabrication of free-form timber components, for where precision cutting was needed. There were also large gaps, including parametric modelling, which would arrive over the next few years. For Haesley Nine Bridges, they worked with early free-form software - “possibly the pioneer’, Strehlke notes, adding that the software’s sources are really in that one-time architectural moment, Blob architecture, which was, Strehlke opines, enabled by graphical software. At first it brought forth monsters. Now there are monsters and angelic beauties.

Swatch's glulam's from screen-face to site

The link up with Ban proved particularly fortuitous internationally, but also accelerated new   paths in their home country, with the Japanese architect commissioned to build the Tamedia HQ in Zurich, followed quite soon after by the Biel Swatch buildings. On each, Blumer was the engineer and Blumer-Lehmann the timber contractor, with a broader partnership-network of close-knit colleagues, connected in one way or another to Blumer and northern Switzerland’s timber engineering scene, including SJB Kempter-Fitze, and Design-To-Production. Tamedia opened in 2013, and seemingly in its wake other projects began flowing in, resulting in the run of projects completing in 2019. For Lehmann, this achievement isn’t so much a ‘wow’ moment as “a general evolution” which has brought with it technical challenges, but nothing that Lehmann considers radically transformative. At the heart of their step into free-form was the development of a collaborative parametric planning tool, allowing all those working on projects to share the process step by step. The arrival of parametric design, a revolution of sorts in working methods, and one of construction’s buzz digital phrases of the last half dozen years, allowed every step, from detailing, through to manufacture and milling, logistics and assembly, to be planned in virtual space, with all the different team members able to input and work on the shared planning together. Any change ripples through the entire parametric plan, considerably assisting the level of complexity that projects with individual bespoke glulam pieces in their thousands, require. To date, the Swatch gridshell has been the most complicated of these projects, though in an interview Blumer Lehmann’s Richard Jussel, claimed that this was “only the beginning.”

Container land: Lattisch provides forty five affordable temporary workspace
in B-L's local major city, St Gallen

Still, the free-form projects comprise only a minority portion of the Lehmann Group’s portfolio. “In Switzerland we have this saying,” Lehmann says near the beginning of a Skype catch up call a year after my visit, preparing the way for a meaty metaphor. “We work at the two ends of the sausage. Free-form is absolutely at one end. At the other is the standardised, prefabricated modular units that go to make up a chunk of annual output. Beginning in 2005, Blumer Lehmann began producing prefabricated components, before starting manufacturing their own volumetric prefabricated units in 2017. Growth has been swift, to around six hundred units annually. This has come on the back of both reform of the Swiss fire regulatory legislation in 2015 and the strong increase in demand in Germany, which has also seen the take-off of other volumetric manufacturers, such as Kaufmann Bausysteme prefabricated boxes, over the border in Austria. In contrast to the latter, Blumer Lehmann use an element production approach. Prefabrication in schools in both Germany and Switzerland have been one building type, where quick construction times have been prized. Although the prefabricated units are used across smaller non-domestic building types, such as Scheibler & Villard Architekten’s recently completed Swiss Centre of Competence for the Deaf and Blind and Lattich, a 45 unit affordable temporary workspace for St Gallen’s creative communities, this time designed by bauburo in situ. With 1500 schools needing replacement buildings or upgrades across the country it isn’t surprising, though, that 80% or nearly 500 of the volumetric modules churning out of Gossau are bound for schools, Lehmann noting that they have focused on the sector as a specialism. Connecting the modular and the free-form is digital technology; the same joined up prospectus that makes parametric planning such a potent instrument in free-form, is brought to the automation of the timber factory floor. Taken together, the Blumer Lehmann operation felt like Swiss digital and timber tech prowess cross-hatched and happening across a single site. Is Erlenhof a sample of the tech-upped timber future, the messy innards of a 21st century timber yard, the log stacks, steam and sawdust, which don’t disappear inside the screen, even as gleaming parametric and other programming turn much of the master carpenter’s processes into augmentation and following up computational organisation and systems? Automation is the common strand of both free-form and prefabrication, a trajectory which is surely set to grow. These serial waves of technologisation were the region’s response, after all, to the disappearing viability of old style carpentry and timber construction. In Switzerland, as much as the rest of timber’s sub-Alpine silicon valley networks, the industrial timber sector has hardly given any quarter to that past, and Blumer Lehmann only reflect what is happening right across central Europe, the ramping up of industrial timber construction at every opportunity.

Lehmann Group's Silobau include the Uitikon saline
silo outside Zurich, and right, Western
Switzerland's Domdidier silo plant

All this said, the two-part third strand to the operation sits, at least to the innocent eye, somewhat oddly with Blumer-Lehmann’s avant-timber reputation; the manufacture of gritting silos and supply of wood pellets and briquettes. Both are hived off and operate under separate company titles, BL Silobau and Lehmann Holzwerk AG for wood energy - with over a 1000 silos (including a special focus on timber silos) delivered, including hi-tech, fully automated, modular and other types, as well as control systems and data processing. For architects visiting and admiring the Cambridge mosque or Helen & Finance Park, this is likely the lesser-known side of Blumer Lehmann. Still, at least one of these salt silos, the Uitikon yard outside Zurich, featuring a spreading silo, warehouse, and washing hall, exhibits a cool timber design aesthetic.

As we made our way over to a large shed that houses all the free-form timber preparation and manufacture, the connection between the sophisticated geometric forms and timber’s more basic origins was piled up there and only too physical, great stacks of logs in front of me, fuel for the highly automated sawmill. According to the website, around 150,000m3 of logs pass through the sawmill annually, mainly sourced from forests lying within a hundred kilometre radius. Lehmann’s do not own forests themselves – “we don’t slaughter the trees ourselves,” Lehmann jokes, rather buying from regional forest owners, many of whom are either canton operations, or private woodlands. Like the rest of the timber sector, this is very much a business operation, any thinking otherwise is naïve. The most recent financial statement of Blumer Lehmann’s I could uncover stated annual turnover of £11 million. It is likely larger: the company is expanding, with plans to enlarge its factory site. There is a relatively new German office satellite, and a busy order book. At the same time, it is also clear there is a curiosity towards and a form of personal allegiance to wood, and to its 21st century possibilities. “Wood,” says Lehmann at one point during the visit, “has got an energy which we should really use. And it has intelligence as well. There is another dimension there.” If this isn’t quite world wood web territory Lehmann is, at least to an extent, acknowledging the possibility of mystery among the trees.

On the one hand this has drawn the company further into wood materials research, primarily with ETH-Z Wood Materials researchers who are working at the nano-scale, specifically on research into cell structure modification. This has begun to feed through in cellulose experiments and the first live projects and material applications. On the other hand, there are more mainstream concerns, particularly the increasing worries over Alpine and central European forests. With the rise in mean temperatures and the longer drier summers stressing various species, particularly the main productive tree, spruce, worries are only increasing across the sector about the source of their materials. Added to this is what is known as Forest Death 2.0, Waldsterben 2.0 (Waldsterben 1.0 was the acid rain pollution of the 1970/80s) particularly spruce forests’ nemesis, the bark beetle, which has thrived in the warm weather through the last three summers, eating into and leaving a trail of destruction and a swathe of dying forests, and parts of the forestry sector in jeopardy in all three DACH countries.

Deathly Waldsterben 2.0 – Photo Pixabay

These multiple forestry crises have brought on an increasingly agitated debate across the German language countries regarding what is to be done, splitting into an updated contemporary variation of  German Green political Realo/Fundi’s (or Pragmatic Realist/Fundamentalists) divide between a predictable pragmatic, commercial mainstream and more activist, and in contemporary hue, rewilding camps. It is clear where Lehmann stands. There is a need to change, she acknowledges, but she believes the activists’ arguments are too simplistic. “We understand that the forest will not remain the same with climate change,” she begins, before noting the efforts to mitigate the consequences of warming weather and climate pattern. Switzerland’s forests are becoming more diverse, sustainable forest management requiring a much broader forest ecology of different species of hard and softwoods. “The forestry owners haven’t got so much older species, which they can easily sell, only spruce and fir.” Rewilding and other nature activists who demand that the level of forest diversity needs to encompass forty or more different species, are being unrealistic, Lehmann observes. She doesn’t agree with those, including the rewilding community, who say leave the forests to be, that if you don’t do anything, nature will just do the necessary repair work. “It’s not possible,” she says bluntly. Sustainability for her is ecological, social, and economic, emphasising the last in this green trinity. “If you ignore the economic there isn’t any economy to do these changes,” before pointing me to an interesting, though orthodox, industry-perspective essay in the German media by academic Roland Irslinger (in German).

Unlike many architects, though, Lehmann sees through the weaknesses of simply measuring individual building footprints. Knowing the amount of carbon locked into a building is pointless, she believes; as a statistic on its own it is tantamount to being meaningless: you need to look at timber at a geographical level, and you need to look at it as a system. The legitimacy of the carbon footprinting is critical too, needing to be part of Government programmes and “not just timber companies’ marketing.” Regulation is coming she says, referencing the publication of EU position papers. Every action, she says, is laced with complexity, but (she implies) there’s a big shift on the way in managing forests.

Wood fibre at the nano level – Collage images::
ETH-Z/Wood Materials Institute

I couldn’t help but wonder if these moves weren’t reactive rather than proactive, however; we were talking before the Australian, Californian and northern Swedish fires through late 2019 and into 2020 had spread doomsday images across the internet. While the bark beetle was doing for Swiss Spruce, higher temperatures and longer drier Alpine summers are sources of broader species stress for hardwood species, particularly beech trees. Across the Continent, stocks of unused and damaged hardwoods stack up, with many across the sector wondering what will be next.

For Lehmann this was one way their collaboration on the chemical modification of woods could potentially be practical, the research offering solutions for using the increasing reserves of hardwood. This was also the case with their own current R&D, a coating spray helping the wood’s original colour resist deterioration. “It’s the perfect product,” she says happily, even if it had hit a possible hurdle as the nano-particles are exposed to a new batch of regulations.

From below - the Urbach tower, and below the kiln drying and preparation of the curved CLT
– all Urbach tower photos ICD/ITKE University of Stuttgart (and Empa/ETH-Z, for photos below showing development process)

The wood material modification research project which has advanced most fully to date is the collaboration with Zurich’s ETH Wood Materials Science unit, the Swiss Materials Institute Empa, Stuttgart’s Institutes of Computational Design and Construction (ICD) and Building Structures and Structural Design (ITKE), which has resulted in the world’s first curved Cross Laminated Timber (CLT) panels. The researchers developed computational models to simulate the hygroscopic properties of timber at the cellular level, before calculating the amounts of moisture each grain would require so that wood ‘self-shaped’, shrinking or swelling into the required shape of the curved panels. A live project - a timber tower in the small Baden Württemberg town of Urbach as the test for twelve laminated panels - was prepared at the Blumer-Lehmann factory before being transported to the site and installed.

You can see the attraction of curved CLT for Blumer-Lehmann, offering another material option for their free-form projects and the potential of the novel hygroscopic approach, given the increasing geometrical complexity of timber design. Still, listening to Lehmann, their involvement sounds almost quixotic, as if curiosity got the better of them. It was, she says, “hard to say no.” They went into the research with eyes wide open that the outcome was likely not to deliver immediate commercial outcomes, which indeed, is how things panned out, a project in search of a sound reason.

“It was difficult to do. From the beginning we didn’t have an interest in the material commercially. It was a thematic model, and to do with the problems, and how it may bring surprises.” For now, the 46 foot tall Urbach tower stands - a solitary harbinger to a possible future curved CLT.

There were several pieces of the free-form engineered timber in various stages of preparation in the warehouse when I visited. Strehlke, unsurprisingly, wouldn’t say who their current projects were with. It was quiet though, the tech and machinery switched off, and only a couple of carpenters present. One piece of machinery bore the legend Techno-Wood. Great arched glulam beams were waiting for the next stage of preparation. Some mock-up test pieces stood including one of Ban’s Haesley timber tree columns, and, on one of the hall’s walls, the lattice system. It was from here that the free-form timber revolution had been launched. One can count almost on a single hand, definitely two, the number of companies who are at the heart of this part of the 21st timber edge. A few names come to mind, Wiehag, and Züblin Timber, who bought out Blumer-Lehmann’s arguably closest comparable operation, Merk in Bavaria’s Aichach, many years ago, and both much so much larger-scale. If one considers that free-form has primarily arrived in the last fifteen years, it’s tempting to telescope – with or without hygroscopic curved CLT - into the next fifteen and envisage new chapters in the revolution. As it is, Blumer Lehmann’s place, when the history books begin to recount the chapter, feels assured.