People had known that wood burns before they were able to build a house – fortunately. The combustibility of wood does not change, yet it is possible to build high-rise buildings in wood in Switzerland nowadays – is it safe?
The images of the burning roof truss of Notre-Dame in Paris are still vivid, thus many people cannot help wondering whether the contemporary buildings should still be built in wood? The answer is clear: Yes, do not only think timber construction companies but also the experts at the Association of Cantonal Building Insurances (Vereinigung Kantonaler Gebäudeversicherungen, VKF). As the umbrella organisation for building insurances in Switzerland, the VKF is responsible for Swiss fire protection standards. According to the latest VKF standards, which came into effect on 1st January 2015, timber construction should meet the same building codes as other construction systems such as reinforced concrete construction. It has built the Swiss standard to become one of the most advanced fire protection standards in Europe. Today, buildings up to 30 meters (approx. 8 storeys) can be built in timber using a standard concept. It is also possible to realise high-rise buildings up to 100 meters in timber with a special fire protection concept.
Fire resistance, not combustibility, is decisive
Today, the fire resistance of a construction is decisive in the fire protection of a building, not the combustibility of a building material. The most critical step for fire resistance is to assess the load-bearing capacity of a structure, i.e. how long it will take until the structure collapses. The second important factor are the fire compartments that prevent the spread of fire and smoke over a certain period of time. Thanks to the intensive research work and tests conducted at various institutes in Switzerland and throughout Europe, the fire resistance of each building material and the entire constructions can be calculated precisely now.
Most important is to ensure the safety of humans and animals
The objectives of fire safety regulations are firstly to ensure the safety of humans and animals, then prevent combustion and explosion and limit the spread of flames, heat and smoke. To prevent the case of fire for good is hardly realistic. However, it is possible to design the fire resistance properly for all types of constructions, so that people and animals can leave the building safely and timely in the case of fire.
14-cm thick wooden ceiling lasts 60 minutes in fire
Unlike many other building materials, wood can form charcoal when it burns. This char layer can act as an insulation layer to protect the wood inside and thus slow down the burning rate significantly. This characteristic property of fire resistance makes it possible to build timber constructions. For example, a 14-cm wooden thick ceiling can last for 60 minutes in the event of fire.
The right construction counts
In addition to the choice of building components, special attention should be paid to component connections in the timber constructions. The timber engineers can offer various standardised details and calculations in these fields. Through the close cooperation between architects and fire protection planners, detailed solutions can be developed early in the planning process and quality control can be guaranteed throughout all construction phases. Today, timber construction projects can be planned, developed and realised safely and easily, meeting the high requirements of the VKF standards.
The market has recognized this development. Countless timber constructions have been planned and built worldwide safely, efficiently and environmental friendly – and more are yet to come.
Additional information
Fire test: wooden house vs. ordinary house (Video in english, see below)
