2,000 cubic meters of laminated spruce, from certified Austrian forests, that the Pritzker Prize architect, Shigeru Ban, has personally selected by specifying its type, its origin (from spruce trees above 1,000 m), growth (slow, in order to have a greater stability and with the rings of the trunk very close to each other).

Seen in cross section, the building has three bays in total, 2 of which are terminals by modest lights, amounting to 3.2 m each, in contrast to the central well of 14 m, which excludes the use of intermediate supports for a total development of 20.4 m. The vertical elements, of a height equal to five floors, have been erected in situ through the use of a crane and solidarized by inserting transversal bars in oval section of 5.5 m long and 35 cm high, in order to prevent the rotation of the façade.

The structural junction nodes between the floor and the vertical structures that support the double- façade, in a curtain wall and an inner, solves the connection by using of wooden beams coupled into the end spans, with a height of 56 cm and section 20 cm. The beams, primary Vierendeel type and secondary, are laminated with a rectangular section, and are arranged according to an orthogonal grid. The horizontal elements are also made of wood, and subsequently to their laying they proceeded to the placement of the glass façade.

Not only the columns (square section of 44x44 cm) and the beams, but also the connections are common wood: instead of bolted flanged joints or additional steel, special anchors in plywood beech were used for the transmission of the load and the strengthening of the constructive elements. This structure was assembled on site by the use of precast products with CNC milling machines, with accuracies in the order of a millimeter. Great care has been taken to prevent the risk of fire and collapse of the structure, oversizing to this purpose the elements with a layer of sacrifice equal to 42 mm, meaning that the layer of wood that can burn for 60 minutes.

The 1,400 structural elements that make up the construction have been transported to the site during the night, by the use of trucks, in order to ensure the immediate mounting the next morning, avoiding possible problems to vehicular traffic. A real own architecture, therefore soft tech, high of 21 m and weighing nearly 20 tons. Opened in July 2013 on a concept developed in 2008, is the first building to be designed by the Pritzker Prize winner, architect Shigeru Ban; will not be the last, expectant for the new headquarters of Swatch, ready by 2015.

Ban has designed this wooden structure that is inspired by traditional Japanese techniques used by carpenters of the Rising Sun, reviewing in a contemporary way, particularly those of "Miya- DAIKU" and "Sukiya-DAIKU." The first, characterizing temples and shrines, are famous for their fine wood joints, while the latter, adopted for the construction of homes and tea houses, opt for the aesthetic use of rustic materials. The load-bearing timber components are simply interconnected and their unions are stabilized by a secondary structure.

These techniques seem to have their roots in the ancient Japanese game Chidori. Similar to the famous Chinese game of "Shanghai", by interlocking dry strips of wood with a square section, allows the construction of modular structures in spatially extended regular mesh. Among the designers fascinated by this ancient "mathematical iteration" born for recreational purposes, there is Kengo Kuma, who has developed this spatial grid in suoChidori Cafe, in Fukuoka, for the well-known international chain Starbucks in 2011.

The double façade acts as a thermal interspace and helps the natural ventilation of the building. 50 meters long, has excellent insulating properties, as it has low-emissivity glass, as well as meeting the requirements for EI60 fire protection. The heating and cooling of the complex is via the geothermal groundwater, without carbon dioxide emissions resulting from fossil fuels. The use of the same wood greatly reduces the environmental impact of CO2 released into the environment: think that 1 m3 of concrete releases about 1,200 kg of CO2, compared to only 150 kg of CO2,  generated by 1 m3 of wood construction. A good thermal insulation and the use of heat pumps allows to contain the costs of maintenance of the first multi-storey building in wood present in Switzerland, whose total amount is approximately EUR 40 million.

 

Details of the project

 

Project Architect: Shigeru Ban Architects Europe (Paris)

Project Leaders: Kazuhiro Asami , Gerardo Perez , Takayuki Ishikawa , Masashi Maruyama

Local architects: Itten + Brechbuhl AG (Bern)

General Contractor: HRS Real Estate AG (Frauenfeld)

Enterprise for carpentry wood: Blumer -Lehmann AG (Gossau)

Structural Engineering : Creation Holz GmbH

Plant engineering :3 -Plan Haustechnik AG

Floors: 7+2 basements

Workstations: 480

Building's floor area of : 8,905 square meters

Building volume: 39 085 cubic meters

Construction wood used: 2,000 cubic Spruce laminated