A shingle facade in the middle of Lucerne
05.04.2023
The Liv Suites in the seven-story wooden building in the heart of the city of Lucerne offer a modern living experience. The shingle facade is an eye-catcher. Fire tests allow the continuous larch cladding without disturbing aprons or fire bars.
In the urban context, masonry, glass and stone are the dominant materials for facades. In most cases, these materials are not specified in the building regulations, but architects and developers must nevertheless argue well if they want to realize a new building with a wooden facade in the city center. Tobias Schaer, owner of the property at Maihofstrasse 8, together with FANGAN Architekten, succeeded in convincing the city to build an apartment building with a shingle facade.
Maintenance-free facade
Now the seven-story wooden building is completed and the larch shingle facade shines with its golden yellow color. Soon it will take on a silver-gray patina and is very durable thanks to the natural resins and ingredients. The facade does not require maintenance or painting and has a service life of up to 80 years.
Images: burkart.lu Fotografie
The new building on Maihofstrasse with its seven floors is located below the high-rise building limit. Nevertheless, measures must be taken for combustible facade envelopes of three stories or more to prevent a fire from spreading over more than two stories. At present, there are still no principles (e.g., from Lignum) on the state of the art for shingle facades that specify the design principles for fire protection. Therefore, the measures must be derived from proven design principles of similar wood facades as well as from past experience, for example, fires on shingled buildings or fire tests.
Shingle facade without aprons
Shingle facades are particularly aesthetic when they wrap around the entire building without being interrupted by aprons and fire bars. It then remained to be judged whether a fire would spread outside at an inadmissible rate or "self-climb". The spread of flames depends on the dimension and layering of the shingles as well as their deformation behavior. For the new construction of apartment houses Wolf and Edelweiss in Andermatt Timbatec determined the fire behavior of such a facade in fire tests.
Green light after fire tests
The facade on Maihofstrasse is constructed according to the same principles, and the general conditions for the Wolf house and the Liv Suites building are comparable: Perforated facade with windows on top of each other, no inside corners, standard distances to neighboring buildings, non-combustible covering at the base level, location in the middle of new buildings that are also state of the art, and a maintained facade. The results of the fire tests from Andermatt were therefore allowed to be used for the construction in Lucerne and made the shingle facade possible for the Liv Suites building.
During the tests in Andermatt, an initial small-scale fire test on a sample served to roughly assess the fire behavior. In a second step, a real fire test on a piece of facade followed in consultation with the authorities.
By 15 minutes after the outbreak, the fire had spread across the facade to a height of about 4 meters. After the supporting flame under the piece of facade was reduced again, the spread on the facade also stagnated. After the support fire was extinguished, the facade continued to burn in the partial area of the fire cone, but spread to the undamaged area was slow. With the type of shingle tested and the fire protection measures taken, the defined protection goals can be met.
Parties involved:
- Architecture: FANGAN Architekten
- Timber engineer and building physics: Timbatec Holzbauingenieure Schweiz AG
- Concrete structural engineer: PlusStatik GmbH
- Photography: burkart.lu Fotografie
Services Timbatec:
- Structural analysis and design
- Fire protection, especially planning of the shingle facade
- Building physics