Burkard Meyer Architects, Baden (CH)
In the village of Rotkreuz in the Canton of Zug, construction is currently under way on a carbon-neutral development that includes residential units, offices, retail outlets as well as number of leisure facilities. The Zug Estates Group is investing around 450 million Swiss Francs in this project, which located on a former industrial site known as Suurstoffi. After completion in 2020, the site will have 1500 permanent residents, will offer workplaces for 2500 people and will house 2000 students of the Lucerne University of Applied Sciences and Arts.
The main building and landmark of the complex is a ten-storey office block in a hybrid timber-concrete construction. It consists of two distinct, interlocked sections, namely a tower structure that overlooks the site and a lower section whose height corresponds to the adjacent buildings. The office floors have an open-plan layout and can be reconfigured as required. The interior is characterised by an interesting combination of exposed timber and concrete elements. For the façade, the designers opted for a matte Alucobond cladding.
Planning permission for was granted for this -the first midrise timber block in Switzerland- in July 2016, and construction commenced in August of the same year. The project was completed in 2018. Given the height of the building, the timber used in its construction must meet exacting structural strength requirements. The tight construction schedule also demanded great precision, something allowed by contemporary wood structures.
The composite timber-concrete floor elements are manufactured by Erne Holzbau AG with its patented construction system (ERNE Suprafloor ecoboost 2). A12 cm thick concrete slab provides the necessary compressive strength and ensures fire resistance and sound insulation. Under the slabs are downstand beams in spruce measuring 16 x 30 cm, installed at intervals of 100 cm and fixed to the concrete slab by means of shear-resistant perforated sheet metal elements, thereby providing the required tensile strength. As a result, the use of reinforcing steel is minimised, which is one of the main reasons behind the excellent CO2 footprint of the project. This building method also shortens the construction time by around four to six months, as the individual floor elements (including an integrated heating/cooling system) are delivered as prefabricated units to the site.
The main beams and columns are made in BauBuche GL70. Thanks to the excellent compressive strength of the material, the cross-section of the internal columns is only 34 x 34cm. Equivalent posts made in softwood glulam would have to have cross-sections more than twice as thick. BauBuche therefore creates not only a more elegant construction, but also increases the useful floor space by many square metres. In addition, the structure has a hardwood outer layer. Patrick Suter of the board of management of Erne AG Holzbau calls BauBuche the “Rolls Royce of timber construction materials.” Given savings in material of more than 50%, the costs for the BauBuche structure are about the same as for a conventional glulam construction.
Client: Zug Estates AG, Zug
Project architects: Burkard Meyer Architekten BSA
Construction engineer: MWV Bauingenieure AG, Baden
Timber construction: Erne AG Holzbau, Stein
Fire engineer: Makiol Wiederkehr AG, Beinwil am See
Wood species: spruce
Location: 6343 Risch-Rotkreuz, Switzerland
Category: administrative building