Two offset cubes lie on a two-storey, fully glazed base with a framed design and almost appear to be floating. The glass aluminium facade rises above the foyer with a strict grid shape diffused by cut-out sections that reach two storeys in height and simultaneously serve as outdoor terraces on each floor. The building was erected between 2018 and 2020 and houses the new Service Centre for the City of Minneapolis situated on the Mississippi in the Midwestern US with approximately 420,000 inhabitants. 

Combined with the neighbouring City Hall which was built some time ago, the impressive new build offers a central campus with offices and administrative space over more than 35,000 m² (380,000 sq ft). The new building consolidates around 1,500 members of staff of the City of Minneapolis who were previously spread out over multiple locations in the city centre. Floors 1 and 2 located above the two-storey foyer with its transparent design contain the service centre for public affairs. Floors three to nine contain offices for municipal employees while the top floor serves as a communal employee area comprising terraces and green roofs. 

As the winning team of a competitive process, local architects at MSR Design (Meyer, Scherer & Rockcastle) and the architects at Copenhagen-based Henning Larsen say that the new Service Center represents a departure from traditional administrative design with long, dark corridors and closed doors. Accessibility and openness have an inviting effect in combination with the seating areas. The city also invited 16 local and regional artists to design one of the open and public rooms with various works of art, including a sculpture suspended in the lobby and five murals made of glass.

Bright Jura limestone panels were used as facade cladding in addition to a significant amount of glazing and anodised aluminium. The natural stone panels in various dimensions were supplied by VeroStone, a company based in Eichstätt, Bavaria. Attaching these panels to the facade and interior wall cladding over a surface of approx. 1,600 m² (18,000 sq ft) proved to be a tremendous challenge due to the weight of the elements. In addition to the Minneapolis construction company M.A. Mortenson, parties responsible for the application included Larson Engineering (Wisconsin), in charge of technical planning, and the craftspeople at Grazzini Brothers (Eagan). The fischer undercut anchor in the FZP II 13 x 26 M8/VS/4 AL version was ultimately chosen for the task. The anchors and aluminum support system were supplied by PROBE Rainscreen Facade Systems, fischer’s facade systems supplier in the US. 

FZP II undercut anchors enable stand-off installation for all types of natural stone such as granite, marble, sandstone or, in this case, limestone. The constant residual wall thickness used as a reference measurement while creating the drill holes ensures that the panel thickness is compensated. Its sleeve consists of stainless steel. “The form-fitting anchorage free of expansion pressure in the conical undercut drill hole enables higher loads and larger panel formats”, says Steven-Henrik Maier, Market Manager facade systems at the fischer Group of Companies, naming a key advantage. The undercut anchors allow for higher pull-out loads compared to conventional systems while providing optical advantages: “The fastening point is concealed when viewed from the building’s exterior, which provides the facade surface with an appealing and distinguished look”, Steven-Henrik Maier states. As demonstrated by the Minneapolis Service Center, fischer is an all-in-one supplier of rear-ventilated facades. 

The SystemOne Vertical Solution for subframes was also used. The innovative facade system was able fulfil the project’s requirements and lower costs. All system compo-nents were supplied by PROBE Rainscreen Facade Systems, which also provided technical support. “One of the ad-vantages is that it doesn't require horizontal rails to fasten the facade, which saves a great deal of materials and costs”, Steven-Henrik Maier says. “The panels of this subframe solution were installed with the help of the integrated suspension nut of the FZP II VS undercut anchors combined with the suspension brackets attached directly to the vertical profiles of the SystemOne Vertical Solution according to the keyhole principle. The acting dead weight and wind loads are transferred directly via the hook system”. Louisa Tett, owner of PROBE Rainscreen facade systems, adds: “PROBE worked with the architect Byoungin Lee at MSR Design to design a suitable system for both interior and exterior applications using Jura Limestone, which we have used quite successful-ly on many projects. We were able to work nicely with Grazzini Brothers, who was awarded the project, and with Larson Engineering, who provided shop drawings, stone tickets and calculations to deliver a beautiful project.”

The city of Minneapolis has created a citizen-friendly administrative centre with the new building. It will also allow the city to work more efficiently, as its members of staff are no longer distributed across multiple sites, which also saves a significant amount of operative costs. Sustainability was a guiding principle during the construction of the new administrative building, and the city is currently trying to receive the LEED Gold certification by the US Green Building Council.