First multi-storey timber office block in Switzerland

In the village of Rotkreuz in the Canton of Zug, construction is underway for a modern climate-neutral estate 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 located on a former industrial site known as Suurstoffi. After completion in 2020, the new estate 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.

Schweizer Holz-Hochhaus im Detail

The main building and landmark of the new estate is a ten-storey office block in a composite timber-concrete construction. It consists of two distinct, interlocked sections, namely a tower structure that overlooks the estate and a lower section whose height corresponds to that of the adjacent buildings. The office floors come with a uniform layout and can be reconfigured as required. The interior is characterised by an interesting combination of timber and concrete elements. For the façade, the designers opted for a matte Alucobond cladding that gives the construction an elegant look.

Planning permission for the first timber multi-storey block in Switzerland was granted in July 2016, and construction commenced in August of the same year. The project is scheduled for completion in 2018. Given the height of the building, the timber used in its construction must meet exceptionally high structural strength requirements. The tight construction schedule demands highest precision, which is of course something timber construction specialise in. The composite timber-concrete floor elements are manufactured by Erne Holzbau AG with its patented construction system (ERNE Suprafloor ecoboost²) that combines the best of two worlds: a 12 cm thick concrete slab provides the necessary compressive strength and ensures fire safety and sound insulation. Under the slabs, we have dropped beams in spruce measuring 16 x 30 cm, installed at distances of 100 cm and glued to the concrete slab by means of shear-resistant perforated sheet metal elements, 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 that include a new type of heating/cooling system are delivered as prefabricated units to the site.

Rolls Royce at a price of a Volkswagen Golf

The main beams and bearers are made in BauBuche GL70. Thanks to the excellent compressive strength of the material, the cross-section of the internal bearers is only 34 x 34 cm. Equivalent posts made in softwood glulam would have to have cross-sections of more than double that. BauBuche therefore caters not only for a more elegant construction, but also increases the useful floor space by many square metres. In addition, the construction comes with an attractive hardwood finish. That is why Patrick Suter of the board of management of Erne AG Holzbau calls BauBuche the „Rolls Royce of timber construction materials”. However, BauBuche is not as expensive as it looks: given savings in material of more than 50%, the costs for the BauBuche structure are about the same as for a conventional glulam construction. In other words, the proprietor bought himself a Rolls Royce for the price of a Volkswagen Golf!

Comparison of GL24 glulam – BauBuche GL70