The location of the Prime Tower and its two annexes, the Cubus and Diagonal buildings, is part of a formerly almost inaccessible industrial site that is gradually being converted into a business and residential district with associated services. Situated in the immediate vicinity of Hardbrücke railway station and 126 meters in height, the high-rise is the tallest in Switzerland for the time being. It is not only a distinctive feature of the neighborhood, but also a landmark for the up-andcoming district of Zurich West.
The concept underpinning the Prime Tower is of a building that might be said to assume many guises, although its fundamental structure and the means deployed are relatively straightforward. The design aimed to find a floor plan arrangement that would maximize the number of well-lit workplaces, while also seeking to create a striking architectural form evoking differing impressions depending on the position from which it is viewed. The outcome of these efforts is a building on an irregular octagonal ground plan that confounds conventional expectations by broadening toward the top.
In terms of urban planning, the building’s significance is twofold in relation to its impact when seen from nearby or from a distance. From afar, it appears as an abstract, elegant volume formed from greenish glass that changes depending on whether it is seen from the side (from the north or south) or head-on (from the east or west). The planes of the façade, oriented in various directions, reflect the light and the surroundings in different ways, articulating and subdividing the volume into what might be called gigantic “pixel surfaces”. The impression the building makes when seen close-up also changes with the spectator’s standpoint. These close-up views reveal that the projecting portions of the tower exert an integrating effect on the surrounding buildings.
At Geroldstrasse, an inviting outdoor area between the high-rise and the new neighboring Cubus office building leads to the entrance of the Prime Tower and toward the planned Lichtstrasse. In the southwest, a plaza is created in conjunction with the existing listed Diagonal building and the new Platform office building beside the railway.
The ground floor of the Prime Tower houses retail spaces and a coffee bar for use by both office employees and passers-by. Special features on the top floor include a public restaurant, bistro with a bar, and a lounge, while a private conference area is available on the floor below.
The cores and emergency stairs are arranged so that up to four tenants can occupy offices on the same floor or, conversely, one business can occupy several floors with internal atriums and staircases. The projecting portions of the building create additional office space on the higher and therefore more soughtafter floors, as well as providing greater variety when using the space for different types of offices.
The load-bearing skeleton structure of the tower is made of concrete with reinforcing cores. The variously sized cantilevered projections are supported by slanting the supporting columns over two or three stories. The façade is constructed from insulated triple glazing with a greenish tint. To enhance workspace conditions, and to meet fire regulations, which require smoke ventilation, alternating windows can be opened parallel to the building. The prefabricated windows are frameless on the exterior. They grant the polygonal building the multifaceted appearance of a greenish crystal.
