Chipperfield's Kaufhaus Tyrol concrete facade
David Chipperfield Architects was brought in at short notice to work on the Kaufhaus Tyrol retail complex in the heart of Innsbruck’s historic centre. The result is a subtle design that lives harmoniously with its ornate setting.
How do you fit one of David Chipperfield Architects’ cool, spare, modernist buildings into the decorative, baroque heart of Innsbruck, capital of the Austrian province of Tyrol?
What adds to the problem is that the building in question is not some petite cultural trophy, such as the literature museum in Marbach am Neckar with which Chipperfield won the Stirling prize in 2007. Kaufhaus Tyrol is the exact opposite, a huge commercial building of 58,000sq m. Indeed, it is the largest shopping centre in Austria developed at a cost of £130 million.
Well might Chipperfield’s design director, Christoph Felger, call the development “an invasion into a heritage centre by a huge retail elephant”. The challenge had defeated two local architects in earlier attempts. The second of these had scraped through with planning permission, except for its long frontage to the city’s main street. This was, says Felger, “a curved, Zahaesque structural concrete shell that was unaffordable and unbuildable”. By now, the project had escalated into a national cause celebre that was taken up by the head office of Austria’s national heritage department in Vienna.
Chipperfield’s Berlin office was brought in as a firefighter in July 2007, just weeks after winning an international competition for a department store on a similarly sensitive site in Vienna. What concentrated minds wonderfully was the fact that the department store had been totally demolished and new foundations were already being laid. Within two months, Chipperfield presented a new scheme for the facade, and quickly gained the backing of the planning and heritage authorities. And later on, the practice was also asked to redesign the entire front section of the building, the internal shopping mall and rear facade.
The end product, which was completed in March, is pure, undiluted Chipperfield. At first sight plain and simple, the facade sets up a subtle, respectful dialogue with the surrounding historic townscape in a way that integrates the building harmoniously into its setting. And it has been carried out in precast concrete with all the understated refinement and attention to detail for which Chipperfield is famous.
Cool and modernist
In basic terms, the facade to the new Kaufhaus Tyrol is quite simply a repetitive five-storey grid of rectangular window bays in precast concrete – simple, cool and overtly modernist. But it’s not bland and is not another of those flush, opaque curtain walls that envelop so many inward-looking shopping malls.
And there’s no immense shop sign lit up in gaudy neon lights and splashed across the frontage. That’s the first clue that a subtle architectural game is under way in the facade. Chipperfield has picked up several motifs and underlying themes from the ornate, irregular historic townscape of Innsbruck city centre and subtly reinterpreted them in a stripped, abstract, contemporary form.
The first subtle twist is that the facade has been folded into three sections that are cranked at a slight angle to each other on plan. The top floor is even more angular: it meets the main facade only at its central section and sweeps back from it on either side. This cranked geometry breaks up the huge bulky presence of the retail elephant. As Felger explains, it sets the building in the same league as the surrounding streetscape of small shops and cafés with flats above that were built and rebuilt in irregular fashion over several centuries.
Next, the facade is subdivided into storey-height window bays that are on a scale that is human and relates to surrounding buildings. Though not quite golden-sectioned in their proportion of width to height, the bays appear, in Felger’s words “slender and grand”. And they enclose authentic, clear-glazed, albeit non-opening windows that offer views in and out of the shops on the first two floors and offices above.
The glazing is set a full 800mm back from the front face of their surrounds. This brings three-dimensional modelling and the play of light and shade to the facade. It is explains Felger, a response in reverse, abstract, contemporary form to the ornamental balconies, oriel windows, cornices and other embellishments that project outwards from surrounding historic buildings.
On the rectilinear facade of flat surfaces, such modelling can best be appreciated at an angle. Conveniently enough, the shopping centre stands at the edge of the pedestrianised city centre, where customers approach it obliquely.
The projecting window surrounds are hefty, measuring 800mm across the mullions, giving a traditional sense of solidity while also concealing the window frames tucked in at the back. At the same time the mullions splay outwards, which makes the windows appear larger.
Window surrounds are precast units of a very pale beige-grey concrete that matches the render on several buildings nearby. The precise mix of white cement, white marble aggregate and sand to match was painstakingly arrived at after casting some 60 test samples.
The front faces of the precast window surrounds have been sand-blasted to create a similar texture to traditional render. But the reveals have been ground and polished like terrazzo, which exposes the natural patterning of the marble aggregate and creates a glossy, reflective finish that adds a light and airy touch. They are finished in an invisible anti-graffiti coating.
As for the obligatory shop sign, the name “Kaufhaus Tyrol” has been cut to “tyrol”, reduced in size, cast in bronze and demurely inlaid into the precast concrete mullions flanking the main entrance. In the all-enveloping, superheated world of 21st century consumerism, such refined understatement comes across as cool and classy.
Precast for speed
Since Chipperfield was called in after the first contract packages had been let, speed was of the essence. “The enormous time pressure was part of the reason why we chose precast concrete for the facade,” says Felger. “While the primary structure was being built on site, the precast contractor could already start producing the facade elements off site.”
The contract for 470 precast fac-ade units was awarded to German company Hering International, 16 months after Chipperfield’s appointment. The units were brought to site fully finished and lifted into position by mobile crane after the windows had been fixed.
The precast facade is self-supporting, while the hefty U-sectioned mullion units, some 355mm thick, add stiffness to the slender structural concrete columns on the internal side of the envelope. The precast units were anchor-bolted to the structural columns and separated by 120mm of thermal insulation. The 10mm joints between units are wider than Felger would have liked but gave the tolerances demanded by the structural frame, which was already under construction. On the upper floors, the joints are filled with flexible mastic concealed behind a sand finish, while on the ground floor they are pointed in a near-white lime mortar to match the precast concrete.
“I’ve never worked so fast,” says Felger in retrospect, quickly adding that speed turned out to have its benefits in the end. “Hering make the highest quality precast concrete, and we never imagined that a commercial developer could afford it. But because they could deliver quickly and because the recession brought prices down, we managed it.”
Architect David Chipperfield Architects, Developer Signa Holding, Structural engineer Brunnsteiner Ziviltechnikergesellschaft, Facade consultant Fassadentechnik, Construction manager ICM Management, Precast concrete contractor Hering International, Precast concrete installer Stoll, Glazing GIG Fassaden