Ruby Zurich – Conversion of the Office Building Du Pont

Client PSP Properties, Zürich
Architects monoplan, Zürich
Planning 2017-2019
Execution 2019-2020
Services Structure and excavation:
Design phase
Tender documentation phase
Execution phase
Topics Structural steelworkIndustry/tradeTimber constructionRefurbishmentConservationConcrete construction

PSP Properties AG intends to upgrade the existing building and convert it into a hotel.

The two-wing building, constructed in 1912/13, is part of a building complex with an inner courtyard and consists of a basement, ground and mezzanine floor, as well as six upper floors. The supporting structure of the building consists mainly of reinforced concrete ribbed slabs which are supported on beams and rest on a column grid. The building is listed in the inventory of protected objects of art and cultural history. Selected elements of the building, namely the façade and the supporting structure including the reinforced concrete ribbed ceilings are subject to preservation order. Therefore, the existing load-bearing structure is basically maintained in the course of the conversion and, where necessary, reinforced.

The slender ribbed slabs are reinforced by a thin 40 mm overlay of Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) layer on top of the existing slab. The suitability of this reinforcement concept was confirmed by load-bearing capacity tests at the Swiss Federal Institute of Technology in Zurich (ETHZ).

In the Waisenhausstrasse wing, the existing cinema hall will be replaced by a new ceiling and a mezzanine floor. The ceiling above the basement and the floor slab including the foundations will be replaced in order to transfer the greater loads into the ground. In the Beatenplatz wing, the loads are cumulated, hence special reinforcements of the existing support structures and various static interventions are planned for the installation of a building services platform in the top floor. The flat foundation in the basement will be retained and locally reinforced with additional micropiles. The access section will be completely replaced. The new walls and the doublings in the intermediate section serve (together with the doublings in the wings) to absorb the horizontal effects of wind and a potential earthquake. The whole building will also be fire proofed.