Apartment Building on Albulastrasse, Zürich

The project
In Switzerland, buildings with a total height of over 30 meters are considered high-rise buildings. By law, such buildings must be constructed with safety stairwells. This means that all vertical escape routes must be specially protected against the ingress of smoke and fire. If access for the fire department is impossible in the event of a fire, as is the case with the apartment building on Albulastrasse, even buildings under 30 meters in height must be designed with a safety stairwell. The same applies to hospitals. Until now, such stairwells and escape routes were typically constructed of concrete. Not so on Albulastrasse in Zurich: Here, the stairwell was constructed using cross-laminated timber and enclosed with 18-millimeter-thick gypsum fiber boards—encapsulated, as experts call it.

Construction Method
The basement through the first floor are constructed using solid construction methods. The upper floors of the building, which house the apartments, are constructed using timber framing. Conventional timber elements were used for the exterior walls. The ceilings consist of box-girder elements; in some cases, solid wood ceilings were used for fire safety reasons.

The Challenge
Since no longitudinal facade of the building is accessible to the fire department, a safety stairwell with airlocks had to be constructed. This stairwell and the airlocks were built using encapsulated CLT panels. The remaining ceilings were constructed as box girders and the walls using a frame construction method.