Adding new storeys of wood: New housing potential for big cities
Due to advancing urbanization, there is an acute lack of living space in many metropolitan German cities. An attractive solution for the creation of new living space is the addition of new storeys made of wood to existing buildings. To make this approach more popular, Metsä Wood has launched the architecture competition "City above the City". Among the prize-winners is the Berlin concept "Dachkiez" by Sigurd Larsen Design & Architecture.
Metropolises such as Berlin, Hamburg and Munich are popular centres of economic and cultural conurbations, as they offer many possibilities for an individual lifestyle. Today’s youth are particularly attracted for studying or choosing their careers in Metropolises, even older people also appreciate the comprehensive care and the promising leisure activities arranged in Metropolises. This progressive urbanization trend has led to an increase in the population figures in all major German cities impacting a steady rise in residential space requirements.
The population forecast as per the Cologne Institute for Economic Research (Institut der deutschen Wirtschaft Köln), for example, for Berlin is extremely high: Currently, the city has about 3.5 million inhabitants. By 2035 an increase of 14.5 percent is expected, which will increase the population to about 4 million. As a result, urban planners are increasingly faced with the challenge of countering the steady population growth in large cities with new housing estates. But how can this be achieved if cities are already built on a large scale? One option is to enlarge the area of cities, which has led to unattractive outskirts increasingly becoming the urban core. But is this really an option, if, for example, the area of Berlin is already 892 square kilometers? Not really. An attractive alternative here is the creation of new living space as additions to existing buildings, so the roofs of today become plots of tomorrow.
How big is the storey addition potential in Germany?
A study by B+L Marktdaten GmbH shows that the storey addition potential of German cities amounts to around 100 million square meters. With an annual completion volume of approximately 25 million square meters in German residential construction, the residential space requirement would be fully covered over a period of four years. In particular, addition of storeys using wood as a building material can be a fast and inexpensive solution, especially if the load-bearing capacity of the existing components is exhausted or the buildings are not designed for large loads. In addition, wood is also suitable as a sustainable building material. During its lifecycle, wood has a surprisingly low CO2 balance and can be used in almost every type of building for carbon storage.
Given with these advantages, it is now necessary to motivate the decision-makers in the planning departments as well as housing associations and private investors with the appropriate impulses to make this great potential accessible. The preconditions in the cities are different, but an increasing willingness to develop at an urban development level is evident.
One of the honoured attendees of City Above the City competition
In total, architects from 40 countries designed concepts for 69 metropolises around the world, which were evaluated by an international expert jury, including Stefan Winter, a professor at the Technical University of Munich. In addition to designs for New York, Shanghai and Tempere, the Berlin concept "Dachkiez" was also honoured.
The architecture firm Sigurd Larsen Design & Architecture designed a timber extension for a 270-meter-long residential complex in Heinrich-Heine-Straße in Berlin Mitte. Characteristic of the Heine district is the prefabricated construction of the Sixties, which looks like a Gray concrete desert. Here, Sigurd Larsen Design & Architecture saw great potential for a timber extension with Kerto veneer laminated timber construction, which not only increases the living space of the building, but also places an optical emphasis on it.
"Wood is a lightweight, structurally strong and at the same time well-insulated building material that can be easily processed.In addition, wood is a CO2 balanced raw material, something which is very important to us as architects.The light-weight construction with wood is therefore a first-rate solution for the idea of the Dachkiez: A new village can be built in the middle of the city on an existing residential building without the need for static changes to the existing structure. Instead of building on the popular open spaces, new residential areas can emerge on the looming roofs in a growing city", emphasizes Sigurd Larsen of Sigurd Larsen Design & Architecture.
The "Dachkiez" concept consists of two layers: First layer constructed directly on the existing roof, a green park will be built in full length of the building, which is accessible barrier-free as a local recreation spot for all residents. On top the new wooden living units, which extend like a sprawling village on the entire house length of 270 meters and highlight the horizontal orientation of the building. They are made entirely of Kerto laminated veneer lumber and are based on a modular system, which can be composed of up to three elements, depending on the housing needs: The standard module consisting of common room, bedroom and a bathroom which is suitable for singles and couples. A supplementary plug-in module which ensures more space with an additional bedroom, ultimately makes the apartments suitable for small families or residential communities.
A third module offers another extra bedroom and enlarges the bathroom space, so that even larger families can accommodate with enough space. Characteristic of these apartments are large windows with a breathtaking view of the Berlin skyline. The juror Prof. Dr. Winter explains the peculiarity of the winning project as follows: “Dachkiez, the village on the roof, creates is a new village with enough space for social development, art and creativity. At the same time, the existing regular structure of this kind of industrial buildings are included in such a well planned and detailed project.
"The "Dachkiez" concept evidences that the integration of timber additions to existing buildings can be a significant solution to the increasing housing shortage in urban centres. In the future, this approach should be given more consideration, as it not only aims at creating more living space quickly, but also make metropolises more sustainable and liveable.