Undisturbed marble shine- thanks to invisible fastenings

The Zurich-based architectural firm Office Haratori and the architects from Office Winhov in Amsterdam were responsible for the design. The planners were also able to express the client’s field of activity in the architecture. The renovation of the building and the newly constructed marble facade in 2017/2018 integrate the commercial building into its surroundings. In addition, the renovated commercial building also represents consistency, timelessness, innovation and perfection, the “core business of the Bucherer company”, according to the architects. While the ground floor is all about the material bronze, the carefully arranged marble plates characterise the floors above it. The stone comes from Switzerland’s only marble quarry in the canton of Ticino. “We refine the marble from Vallemaggia into precisely crafted, jewellery-like elements,” says the Haratori office about the design. "The facade becomes – similar to a sunclock – an image of the current times of day and year. The marble relief is in the changing shadow pattern, sometimes soft over the entire surface, then sharp and orderly."

The facade consists of approx. 100 different steel tubular lattice structures, fitted with conical marble pieces of 6 to 18 cm thickness in various sizes. These components have been prefabricated into elements at the factory. Later, they were hung on site in blind assembly on 6 to 8 pins. The individual weight was up to 4.5 tonnes. Placing such heavy elements with an off-centre centre of gravity so accurately that all pins were hit was a major challenge. Especially because the steel elements were not flat, but deformed by up to 10 mm, which is inevitable in steel construction. This hurdle could only be overcome with a suspension device designed specifically for these elements. The fischer facade systems division of the company group was responsible for fastening the marble panels to the steel structure using undercut technology. The undercut holes were drilled with a tolerance of less than 1 mm. This meant a great deal of effort, as Steven-Henrik Maier, Market Manager of Fischer Fassadensysteme, reports. "Challenges arose with regard to the high loads incurred due to the dead weight of the panels, which were up to 180 mm thick. A few pull-out tests were necessary to prepare for the correct and safe execution." The tests were carried out in different panel thicknesses (30, 40, 60, 80 mm), also close to the edge and with larger panel formats. As a result, a special anchor with a higher integration depth was designed to be able to carry the loads.