Site Specific: Roof Extension T19
ANA - Zurich, Switzerland, 2026
This project, for a new roof space added to an existing tenement building in Zurich, is quiet on the outside but exuberant on the inside. While adding much-needed extra accommodation to this much-loved building, the project also includes playful elements such as the spiral staircase to the uppermost level; suspended from the new roof structure and married to a balustrade of refurbished radiators.
Prior to starting work, both the client group and the architectural practice already possessed sophisticated collaborative approaches to pursuing common aims and this lent itself to the way in which both teams worked together as this project was developed and constructed. The precise but unpretentious way in which materials are brought together seems very apt here, accommodating future adaptation and nicely echoing the plurality at the heart of the building’s social fabric.
ANA This project involves the conversion of the attic space in a cooperative housing project in Zurich that has its roots in the squatters’ movement. Built in 1855 in the working-class neighborhood of Aussersihl, the building was acquired by its current residents in the 1990s. Since then, they have lived in the building collectively at affordable rents – thereby shielding it from the gentrification of the neighborhood. The building was renovated by the residents themselves and adapted over the years to changing needs, most recently through the current roof conversion.
Following the forced demolition of an informally constructed rooftop terrace, the question was how to regain the lost outdoor space. Other factors included a roof in need of renovation and the possibility of adding a story within the building code, provided that the roofline facing the street remained unchanged. The result is an addition in the form of a hybrid roof: the street-facing appearance is preserved, while an additional story is added facing the courtyard. This creates two terraces serving as a shared outdoor space.
Until 1996, the building was occupied floor by floor. Since the Durchbruch cooperative moved in, twelve people have been living together in a large shared apartment on the upper floors. The ground floor houses the Totalbar, whose staff also live in the building. The addition of a new floor creates extra outdoor space, a new common room, a bedroom, and a guest room.
The addition sits atop the existing house like a hat. Aside from necessary fire safety measures and the renovation of the staircase railing, the existing structure remained untouched. The work was carried out while the house was occupied.
The addition is constructed of wood; the interior walls feature a wood-frame structure and are clad with wood and clay building panels. The meeting of old and new remains visible: the former roof slope is visible on the interior walls, as only the newly filled gable triangle was plastered. The old ridge beam was doubled and remains raw and visible. The spiral staircase to the new attic does not touch the existing structure – it is supported by the roof and hangs down into the top floor.
The design process was developed in workshops and working groups together with the twelve residents. They not only contributed to the architectural development of the project but also organized the reuse of building materials and took on parts of the construction work. In addition to ecological aspects of sustainability, resident participation was a key element of the project. Building on a long-standing culture of self-organization and collective construction in dialogue with the architects, we view building as a social practice.