Strategies for more living space

Berlin has grown at break-neck speed for several years. A Berlin Senate report forecasts that the number of inhabitants will grow by more than 266,000 to approximately 3.8 million by 2030. Other cities in Germany, such as Hamburg, Frankfurt, Cologne or Düsseldorf, also exhibit significant growth rates, although not in equal measure in housing construction. Plots are rare, particularly in city centers, and building approval procedures are long. The result: rents and the price of residential property grow dramatically. Political and urban planning solutions are therefore urgently sought to partly offset this development. In the meantime, cities increasingly rely on infill development. This means that exist- ing plots should be used and gaps closed to create affordable housing. 

The cities build taller and tighter. But in the process, one thing must not be forgotten: the quality of the new residential construction and the quality of the urban community. So how can a liveable, thoughtful residential architecture at affordable prices be created that simultaneously results in new urban identities in the city neighborhoods? The Berlin housing association Howoge put this question to selected architects who participated in a limited competition in the form of a tender process for a residential construction project on Paul-Zobel Strasse in 2015. The architectural office of Heide & von Beckerath found a spatial, cost-effective and structurally appropriate answer with their design for two monolithic residential buildings. 

Living communally in the neighborhood 

Spaces such as those on Paul-Zobel Strasse shall now be further developed. Howoge therefore acquired the approximately 4,000-square-meter site several years ago in order to create new housing at moderate rents. Architect Tim Heide, partner in the Heide & von Beckerath office, explains his analysis of the location at the beginning of the design. “In GDR times, such open spaces were intensively used and cared for by the residents in their leisure time. After unification they became more and more overgrown. Today these spaces represent an urban planning problem. We therefore asked ourselves how one can respond to this location with an architecture that acknowledges the existing space and improves the courtyard. We were not simply concerned with infill development. The density that would result from the proposed physical structure should instead bring a new quality to the space. We wanted to add some- thing positive and not simply take the space away.” The latter was a particularly important concern for the long-established residents of the neighborhood. They feared that the small green area where the building would be erected would be taken from them, causing the quality of life in the neighborhood to suffer. The result was vehement protests by the citizens and vociferously voiced criticism. The fears of the residents were very important to Howoge and the architects. One of the key tasks for the planners therefore called for integration of community sup- port into the urban development and architectural

concept. The long-established and new residents should come into contact with each other and the sense of belonging should be strengthened. 

From traditional to experimental – apartments for diverse requirements 

Heide & von Beckerath planned two eight-story residential towers on the site. In each case, the bicycle rooms are housed on the ground floor. A one-story day care center links the slightly offset residential buildings. Among the tasks that Howoge set us as architects was development of new ideas for communal living in addition to classical apartment floor plans,” says Tim Heide. “They could, for example, be shared apartments for single mothers, seniors or students. Our goal was to combine living together individually and communally in these apartments.” Tim Heide and Verena von Beckerath proposed re- serving the mezzanine floor for this purpose. Every apartment consists of a kitchen and a bathroom for communal use. In addition, their own eight to eleven-square-meter room and a small terrace is available to every resident. The terraces are both an open area and private access to the apartments. “This way, one is not forced to use the main access from the staircase,” says Tim Heide, explaining the concept. “These spaces are certainly small, but can be reached separately, which ensures an important element of privacy for each resident. We find such small details important in today’s residential construction.” 

The architects have also considered a special flexibility for the 2 to 5-room apartments on the regular floors. The rooms are arranged around an interior core of bathroom and kitchen. “If the resident dispenses with room doors other than the bathroom, an open, almost loft-like floorplan results around the kitchen/bath element,” says Heide. “If the tenant prefers doors, he obtains many single rooms. They are approximately the same size, so the tenant can determine the specific use. A pretty simple floor plan principle.” Every apartment has at least one private open space in the form of a broad, projecting balcony. Large apartments have up to three balconies. All balconies are the same size, have the same design and are oriented toward the sun’s arc around both residential towers. Each building is accessed by an internal staircase. Approximately 30% of the apartments meet the eligibility conditions of social housing in size and features. 

Ytong and Silka for multi-story residential building 

Special building construction is also necessary to obtain floor plans that are oriented to the needs of tenants. “We wanted a monolithic construction method with no thermal insulation, limited connection details and massive exterior walls that store solar heat,” says Tim Heide. Although they were the same size, the openings in the façade were a further challenge for the support structure, because they were not placed above each other. Since these parameters were already fixed in the competition phase, the architects brought structural engineer Nicole Zahner from the StudioC office on board at the very beginning. “With all of these specifications, it was clear to us at early stage that we needed load-bearing exterior walls,“ Zahner explains. “We decided on large-format autoclaved aerated concrete blocks from Ytong as solid wall construction. We had already used them in smaller buildings. In the two residential towers we calculated the distribution of loads and stresses very accurately be- forehand, precisely in view of the unaligned windows. We absolutely wanted to build this exterior wall design massively, sustainably without ETICS, and at the same time highly stable and insulating. So, highly suitable for residential construction.” Double-pack Ytong Jumbo blocks with a width of 42.5 cm were used for the exterior walls of the upper seven floors. In addition to their excellent insulation properties, they exhibit high noise and fire protection. The ground floor consists of prefabricated reinforced concrete elements. On the other hand, the apartment separation walls are built in Silka calcium silicate blocks, because here sound protection was the primary consideration. Thanks to their higher density, they ensure that less noise and disturbing  sound is transferred between the apartments. Furthermore, the higher load-bearing capacity provides more living space due to the construction with slimmer walls. The load-bearing staircases also consist of calcium silicate blocks. Thus, Ytong and Slika form a great team in multi-story construction. 

The façade exterior received plaster as weather protection and a dark paint that gives both residential buildings a striking exterior and will also promote thermal storage in the massive exterior walls. Inside, the walls are plastered in white. A special color and lighting concept provides a pleasant atmosphere and orientation. 

Xella Deutschland GmbH

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47259 Duisburg, Germany

info@ytong-silka.de

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