Extension in large format



With careful renovation and a large-scale addition, the venerable cardboard and paper mill in the Bern suburb of Stettlen is being transformed into modern living space and a hub for startups and many creative and bright minds. Armin Schawalder will present the project at the Forum Holzbau in Cologne on October 20.

At one time, over 250 employees produced cardboard for the whole of Switzerland. Up to 500 tons of cardboard left the industrial site every day before those responsible shut down the machines in 2010. 

Bernapark AG transformed the former cardboard factory into a quarter with different uses. In doing so, they relied on a differentiated combination of interim use, conversion of old factory buildings and generous additions of new floors. 

The hundred-meter-long factory front along the RBS railroad tracks and Building B, which was set back, had to remain standing. The two structures were carefully renovated, converted into loft apartments, creative spaces and small industrial areas - and extended with a two-story addition. In order to place as little stress as possible on the floors below, the structure was built using timber frame construction. Timbatec was responsible for the structural engineering of the addition, which now houses 133 floor and maisonette apartments. 

Aussenansicht Bernapark

Statics concept

The factory building - a solid structure made of reinforced concrete and masonry - consists of a 140-meter-long beam and a 70 x 40-meter building. Both buildings are 18 meters high and were raised by two floors or about six meters. The elevation must therefore withstand correspondingly high horizontal action from wind and earthquakes. Usually, structural engineers define the points where forces from structures are transferred to the foundations. This is not the case with the Bernapark: Here, the existing building specifies where the forces from the addition may be diverted. This results in a structural design concept with many alternations, different load-bearing directions and, in some cases, large spans. Due to the different vibration behavior of solid and timber structures and the stiff substructure, higher loads were also applied to the timber structure with regard to earthquake resistance. The two additional floors are built in bulkhead construction, whereby the majority of the bulkhead walls are load-bearing and, for building stiffening, are planked on both sides and designed as discs. The ceilings and the roof are mostly spanned transversely as box girder elements.

Statikkonzept Bernapark


Wall construction

The timber construction is also partially visible on the facade: In the area of the terraces, a 20 millimeter thick formwork made of spruce/fir adorns the facade. Other parts of the facade were plastered; they are intended to take up the existing industrial character. In this way, the addition is harmoniously integrated into the existing structure. 60 mm rock wool insulation boards serve as plaster base for the 8 mm plaster layer. Behind this is the actual timber frame construction in the form of 200 mm studs and insulated compartments. On the outside, the construction is clad with gypsum fiberboard, and on the inside with 18 mm OSB boards and 12.5 mm gypsum fiberboard.

Wandaufbau Bernapark

Ceiling structure

Hollow box girders with 280 mm high ribs made of glulam form the slabs. Depending on the span, the width of the ribs varies between 60 and 180 mm. To optimize sound insulation and vibration behavior, the box girders were filled with 100 mm of lime chippings and covered with a classic floor structure. On the underside, the ceilings are covered with 18 mm thick gypsum fiberboard. The ceilings usually rest on the load-bearing bulkhead walls or on internal columns and beams. The spruce columns are painted white and remain visible in the apartments.


Transition apartment balcony  

The roof consists of an insulated ribbed ceiling with the bottom panel as a statically effective surface. The elements of the balconies and loggias, and those in the apartments, were connected with an insulated element joint above the windows. Details: Stuber Holzbau

Deckenaufbau Bernapark

Fire protection and building physics 

Two new staircases in timber construction were installed to provide access to the additional storey. Due to fire protection requirements, these staircases had to be encapsulated and comply with REI 60-RF1. Existing stairwells are of solid construction. The roof also had to provide 30 minutes of fire resistance because the ventilation technology is located on it, the pipes cross several fire compartments and the necessary fire dampers have to function for 30 minutes.



Thun Branch

Timbatec Timber Construction Engineers Switzerland Ltd.

Niesenstrasse 1, 3600 Thun

Tel: +41 58 255 15 10


Zürich Branch

Timbatec Timber Construction Engineers Switzerland Ltd.

Ausstellungsstrasse 36, 8005 Zürich

Tel: +41 58 255 15 20


Delémont Branch

Timbatec Timber Construction Engineers Switzerland Ltd.

Avenue de la Gare 49, 2800 Delémont 

+41 58 255 15 40 


Bern Branch

Timbatec Timber Construction Engineers Switzerland Ltd.

Falkenplatz 1, 3012 Bern

Tel: +41 58 255 15 30



Headquarters Vienna (A) 

Timbatec Timber Construction Engineers GmbH
Im Werd 6/31a, 1020 Wien 
Tel: +43 720 2733 01



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