Interfacing timber cultures – Japan's island forest culture meets Alpine mountain terrain
By TGV the journey from France's north-eastern city of Metz to Switzerland's economic capital, Zurich, is only a couple of hours. Yet, in those two high speed hours, the European world changes from flat Alsace Rhineland to semi-Alpine Swiss lakeside. The 250 kilometres between the two cities also marks the distance between Shigeru Ban's most high-profile European project, Metz's Pompidou Centre, opened in 2010, and the architect's inaugural Swiss handshake, the Tamedia Office block in central Zurich, which opened during the first half of 2013.
The completion of the Tamedia office is also a story of continuity, cementing Ban's relationship with one of Switzerland's leading timber engineers, Hermann Blumer, the man who the Japanese architect turned to when the Pompidou Metz project looked as if it would fall apart – see this Annular Unstructured Hermann Blumer feature. By working together on the Tamedia construction, Ban has not only completed his first Swiss building, as well as Switzerland's first seven storey timber office, he has underlined Blumer's influence on his timber architecture, placing it centre-stage in the country's architectural capital.
Tamedia is the first full building for Ban's Paris-based European studio in Switzerland. This said, the studio has also completed another, largely unremarked, and contrasting interior design: the overhauled Red Cross and Red Crescent Museum in the south of the country (French-speaking United Nations city, Geneva) which also opened in 2013. The country's largest media company, Tamedia publishes popular newspapers like Tages Anzeiger, 20 Minuten and other titles. Its offices had been on the site for over one hundred years, housing nearly 500 journalists and other staff. For Tamedia's majority shareholder, Dr. Pietro Supino, a 21st century building on the same site may have underlined continuity, but he was clear that he wanted it to also speak of change.
– Photo Wikipedia/Public Domain
Needing on-the-ground architects at the time of the competition, Ban invited Itten+Brechbuehl Architects, a Zurich office with a history of collaborating with international firms who had won big projects in and around Zurich. All through the 1990s they had assisted Grimshaw's development of Zurich airport, working until its completion in 2004. In the second half of the same decade they had done the same with Norman Foster on the city's Grand Hotel makeover.
The Tamedia HQ project was kicked off by a limited competition in 2008, which needed to take into account aspects of Zurich’s city fabric sensibility. Despite a few changes in legislation Zurich remains a low-rise city, with a Bau Committee overseeing sensitive applications. A year earlier, aspects of restrictions on high- rise projects were relaxed, which has led to the city’s first genuine tall-ish building, Gigon/Guyer’s Prime Tower, a 126m 36-floor steel, concrete, blue mirror-glass monster in the central downtown Oerlikon district. For the competition, three studios were shortlisted: Berlin’s Hans Kollhoff, and two Zurich studios, EM2M and Bearth & Deplazes Architekten. The last of these, Bearth & Deplazes, submitted a high-rise entry, which, while at odds with the low-rise office orthodoxy of much of the city centre, went on to win the competition. Over the next twelve months, Bearth & Deplazes began developing their winning design, but soon ran into planning problems, its height casting a shadow over a longer area than was legally permitted - more than twenty dwellings.
Tamedia decided to rein in the direction, abandoning the high-rise trajectory, and to start anew with a design that kept to an average six storey height. The new design thinking envisaged the replacement building slotting into the same footprint of the existing building but doing so in a different way to the heavy stone edifices familiar across central Zurich. What if a glass façade, highlighting lightness and transparency, were an option? As it was, Supino had already been making the case for a different approach. "He wanted the right architect for the company because of outstanding work," says Simon Wacker, Itten+Brechbuehl project architect. And he had an idea of who he wanted to do this outstanding project: Shigeru Ban.
the side of the Pompidou Centre, Paris
– Image Shigeru Ban Architects
Supino had seen both the planned Metz Pompidou Centre and the small bamboo temporary office installed on the sixth floor of the Pompidou Paris mothership one day while in Paris and had been much taken with Ban’s relatively off-centre approach. The two began talking, with Ban receptive to the glass palace path, though one with an additional novel element: the structural bones holding the palace up, he proposed, could be in timber.
How very different this would be in a city of stone. Not only the glass palace but - as there was next to no major timber office building tradition in Zurich - there were no appropriate regulations. Any design would need to take this into consideration. Which is why, some months later, when Ban and his Swiss timber engineer guru, Hermann Blumer, unveiled the timber frame skeleton which was to hold the Tamedia Centre up, the glulam posts and beams not only looked like, but actually were, great hefty oversized chunks of timber. The result is a timber system which is at odds with the architectural world’s oft-held desire to achieve structural elements which are as thin and minimal as possible. The system here looks something like it has been put together like chunky Lego-type cellulose members. But these bulky pieces of timber mask the subtlety and intelligence of the timber system that Blumer has brought to bear with the project.
For passing pedestrians, the glass façade enables the curious to peer in and spy the tall timber columns climbing up from ground level. From some distance the timber also stands out, encased in its glass box. Sited at a street junction, with the HQ’s entrance at the front, the building’s V-wing footprint widens along the rim of the two diverging roads. On the near side, the Tamedia Centre looks out over the immediate street, across the Sihl River’s tributary channel on its way to join Zurich’s main river Limmat, and eastwards towards the city’s central built-up island area. On its far face, the road peels away in the direction of the Wiedikon district. In effect an isosceles triangle, with the foyer entrance at its sharp-angle head, the glass façade was initially publicized as a completely transparent space, accessible and appealing to the passerby. In reality, it doesn’t turn out to be quite the same thing, although promotional photographs of the entire building lit up at night makes a good fist of projecting the empty luminescent interior in some style.
Those who look in can see the visible outer skeleton of the timber system standing within the double façade, buffering space between the outdoors and the office floorspace proper. The triple-glazed outer façade is supported by thin steel columns, while immediately inside, the intermediate zone begins with the atrium foyer entrance. Beyond the terrazzo marble ground floor, corridors peel away along the edges of Tamedia’s diverging wings. In the void spaces above are staircases running down from the fourth floor, alternating with break-out lounges, with large lamella windows offering views on the city. With its own micro-climate between outside and interior proper, the open space acts both as a thermal buffer regulating climate and as a protective rainscreen thrown over the glulam columns and frame, ensuring the timber isn’t vulnerable to the weather, the rain or winter snow.
If, when it opened in 2013, the new building was an intriguing sight for the casual passerby (the glass and timber at odds with the stone buildings it is surrounded by), Tamedia also sent ripples through the city's architects. Not only was a large-scale timber office completely out of the ordinary in the city, but the individual structural system left many in the Zurich architectural community scratching their heads - a curious cuckoo in the city's nest. Wacker sums up responses with a smile, "It's not very logical, so it's not very Swiss," before adding that the timber system seems very decorative to the Swiss architectural mentality, with its long tradition of minimal material use generally privileged and often prized. Nor does its materials language connect to the city context, another aspect which has puzzled some observers, even if footprint and form follow the immediate neighbourhood's overall perimeter block sensibility, relating and dating back to its late 19th century's Gründerzeit era beginnings. Ban himself apparently only visited the site once and didn't appear to ask any contextual questions. Cultural differences also became an issue. Wacker recalls the challenges around the staircases. "Small and tight is good to my thinking," he stated, "allowances for tolerances are not." Welding the steel sections of the staircases to each floorplate and the timber structural system turned into a lightning rod for the differences in approach, which were perhaps only unsatisfactorily resolved. Wacker is diplomatic about working with Ban and his team, while conceding it wasn't the easiest of group projects. Early on Ban pushed hard for the façade to extend out from the site's footprint onto the pavement, arguing that this would help with internal climate control. It was the only argument Ban and his team lost. In fact, he apparently confided that Supino and Tamedia was one of the best clients he had ever been commissioned by, and in many respects it appears that the company indulged him almost all of his design aspirations.
For the pitched glazing along the sides of the top seventh floor, Ban wanted the same mechanical flexiglass window system that had been specified for the Metz Pompidou Centre. Designed by Aepli Metallbau – also based, like Blumer-Lehmann, in Gossau, near St. Gallen – the window system turned into a complicated part of the build, and although at 500,000 Swiss Francs per unit, Supino apparently didn’t bat an eyelid, digging into Tamedia’s pockets to accommodate Ban.
Given that the whole building is glass-façaded, an ambitious heating strategy was critical. The louvred external façades and climate barrier was one part of the resulting system, which also relies on significant thermal mass, groundwater heating system and mechanical heating and ventilation systems, moving air around the building for warmth and cooling, and delivered through ceiling cooling panels.
It is the glulam timber frame, however, which is Tamedia’s centrepiece, and it is here that Blumer’s engineering comes into its own. If Wacker had his Swiss reservations about the Ban studio’s design detailing, others have sought to paint Ban and Blumer’s collaboration as a unique combination of traditional Japanese carpentry updated and fused with a particularly Swiss-accented technical sophistication. That the structural system used neither mechanical connections nor adhesives (rather the load bearing elements merely slot and lock into place), has been construed as an example of the Japanese inflection.
- Shigeru Ban Architects
system – Photos and render Shigeru Ban Architects
Running the length of the 38.15m main floor are two rows of eight wood frames, each constructed around four individual posts, set 5.45m equidistant from each other. These two rows of columns, marking each side of the climate buffer space, are joined at each floor by the crossbeam system supporting the main office areas. The columns are mighty things: 21 metres tall, 44cm square, and each weighing 2.5 tonnes. Consisting of three glulam block-bonded timber components, they are also critical for stabilizing the building’s forces, the outer columns acting in compression, the inner ones in tension. The horizontal crossbeams have also been strengthened, two 120mm wide glulam’s stuck together to bring additional strength to supporting the wood frames, extending across the building’s 11m horizontal span. Each of the crossbeam glulam joints have in turn been reinforced by oval beech ply panels. The crossbeams are part of the source of chunky semi-organic expression; they are rounded at the ends where they meet the inner columns before similar shorter beams continue across the remaining outer climate barrier façade. Their chunkiness distracts from the intelligence of the connector detailing. Perpendicular to the crossbeams, rounded (this time oval) spacer beams run the length of both sides of the climate buffer, passing through oval holes cut into the crossbeams, and joining them to the columns. It is a neat yet simple solution, a reference to traditional Japanese timber construction, though also Switzerland’s carpentry history. Were the holes circular rather than oval, the spacer beams wouldn’t grip, but the detail ensures the beams lock together, strengthening the connections. Inside the rounded beam ends is an invisible beech plywood veneer infill addition, again providing extra strength to help carry each floor, as spruce softwood alone wouldn’t be able to: a simple yet elegant solution. The hardwood beech infill is the key to Tamedia not requiring steel fletches and connections, and the connector, where all three components - the columns, crossbeams, and oval spacer beams - meet, is the critical heart of the structural system, the core holding the timber frame up.
These small hardwood insertions instance Blumer’s conviction that engineered beech hardwood can be a critical future timber material. Still, the structural system is overwhelmingly spruce, 3600m3 of the native wood was used, all precision milled and manufactured by Blumer-Lehmann. Another important element was a mock-up of the connector system, which was built at the manufacturer’s site in 2010 so that various tests could be conducted. As it is, the connector, and indeed much of the incredibly precise detailing found across the framework, wouldn’t have been possible prior to CNC (computer numerical control) laser cutting machinery.
For the 21m columns, the largest glulams came from spruce trees growing above 1000m above sea level, on the northern Alpine mountainsides of neighbouring Austria’s Steiermark region. At such heightened altitudes, trees grow more slowly, meaning their annual growth rings narrow, strengthen and improve the wood’s dimensional stability. After their preparation at Blumer-Lehmann’s Gossau factory, they were transported to Zurich, each column going up in a day, as the Blumer-Lehmann team completed the wood frame sections one by one.
Overall, across much of the building’s open plan interior the wood-only structural system has been relaxed and more conventional construction materials creep back into the frame. Raised floors sitting between the bays integrate wood joists, three-layer timber board, gypsum and cement board, as well as nails and screws. Two concrete cores add lateral bracing. And, as already mentioned, welding the staircases to the timber floor plate again used steel. Taken together, these underline the sense that the outer, visible part of the structural system has been used to demonstrate the wood-only engineering of the timber frame. Still, when it came time to calculate the project’s carbon footprint, this came in at 1120 carbon tons according to the Swiss certifiers, the CO2 Institut.
At the column’s sixth floor ceiling, Ban has added a half-height seventh attic floor, sitting under a pitched mansard roof. Shorter timber posts meet slanted glulam struts leaning into the space. This final floor includes conference and board rooms – and impressive views of the Zurich roofscape. The pitched roof is where the Aepli mechanical flexiglass window system has been installed, automatically responding to sunlight and other climate factors regulating the comfort levels across the building.
In all, Tamedia provides 10,263m2 of usable space. It is of course a showcase, the cost, 62 million Swiss Francs, 20% above usual comparable budgets. But when it opened in 2013, Tamedia did provide a new pathway for Swiss architecture to at least take note of. Since then timber, as a less exotic structural building material, has increasingly been appearing in larger and more ambitious projects across the country – as well as, of course, all over Europe. At the time Tamedia was the first example of Blumer’s structural system, a contemporary take on timber framing with glulam playing far more of a central role than much of the more recent CLT (cross-laminated timber) dominated mid-rise timber offices and housing. Blumer has continued developing the structural system - it is part of Ban’s two Swatch office buildings, and most recently, Helen & Hard’s Finance Park – see the Annular Unstructured feature is again a variant on the approach.
If in Blumer, Ban found the engineer he needed for Metz, with the Tamedia project Ban has helped realise what is essentially the engineer’s structural system, and in his home country. The East-West meeting embodied in the Blumer-Ban partnership is as much an individual world culture sampling, expressed in the traditional Japanese joinery refashioned through the Swiss technical lens. Tamedia is relatively modest in height in the cityscape context, and as such illustrates the essentially lower rise realities of working with glue laminated post and beam – as opposed to CLT engineered - timber technology. It is also evident - with or without the Japanese dimension - that Blumer’s carpentry background, his first-hand knowledge of the materials’ physical properties, as well as his conviction regarding hardwood’s potential, is at the heart of how the building stays standing. What isn’t clear is if either the tacit knowledge embedded in the engineering or Tamedia’s general timber-framing principles will be extended and continue to develop after Blumer’s full retirement from the Swiss timber scene. It will be for the future to tell us how this strand of Swiss timber engineering plays out.
This piece is an updated version of an unpublished piece originally written in 2013
