Skyscrapers are back in fashion! Stuttgart has acquired the exclusive Cloud No7 residential tower, Frankfurt has adorned itself over the years with a high-rise skyline and continues to add to it. The tallest building in the Four ensemble is planned to be 228 metres tall, for completion by the end of 2022. This makes it the third-tallest skyscraper in Frankfurt after the Commerzbank Tower (259 metres) and Messeturm (257 metres). In Berlin, along with many other modern towers, the Upper West at 119 metres reaches skyward. In Hamburg, a flagship building in the form of the 235-metre-high Elbtower is to be built as the entrance to HafenCity between the Elbe bridges, by 2025. In Munich planning is looking to the heights. Even if the cityscape of the old town continues to be protected from change by the addition of buildings over 100 metres in the future, this does not apply to the wider urban area of Munich. Especially in the east of the city (between Vogelweidplatz and Messestadt Riem) some high-rise projects are planned or already under construction. By the end of the year, the Bavaria Towers are to be completed, the highest of these some 84 metres tall. An office building 115 metres high is currently being planned, which would be the third-tallest building in the city. Nevertheless, in comparison with projects from other cities, they seem rather modest and thus atypical of the self-image of the capital of the Isar.
These examples alone show that the demand for high-rise buildings is continuing to rise due to progressing urbanization and especially the scarcity, and therefore ever more expensive prices, of land in the cities. But what are the challenges in high-rise construction?
In addition to the strict building guidelines and fire safety regulations in Germany, the height of skyscrapers is also limited by regional guidelines for cityscapes. In Frankfurt, for example, there is a skyscraper master plan, which essentially limits the construction of high-rise buildings to the city’s financial district and the adjoining districts, thus significantly influencing the image of the city and its skyline. In Munich, the building heights were oriented towards the height of the Frauenkirche (100 metres) until the 1980s. Nowadays, this guideline applies only to Munich’s old town. At the approaches to the old town, to the north (Schwabing), west (Donnersbergbrücke / Hirschgarten) and east (Trudering-Riem), an ever-increasing number of skyscrapers have been planned and constructed since the 1990s. In Hamburg too, the traditional cityscape is the focus of the high-rise building plan. The planned Elbtower is to remain the only skyscraper in Hamburg as a striking marker of the entrance to the city via the newly-developed HafenCity, without changing the traditional city skyline of church spires. There is not yet a specific outline plan for Berlin yet, but one should be in place by 2019.
Safety is paramount
In Germany, compared to Dubai (Burj Khalifa 828 metres), the Shanghai Tower (632 metres) or the United States (One World Trade Center 541 metres), no “real” skyscrapers are being built. Most of the time, 200 metres is the limit, which seems almost small compared to the rest of the world. According to the definition, however, buildings of 22 metres and more are already defined as skyscrapers, a consequence of the ladder-length of the fire brigade. Up to this point the fire-brigade can fight a fire and rescue people via a turntable ladder, in addition they must use the staircase and the elevators and extinguish the fire from the interior of the building. A building must be safe for both its residents and the fire service, and with the turntable ladder remaining the sole means of external escape, fire-safety is therefore one of the central issues in high-rise buildings. A tried and tested technique, for example, to keep the elevator antechamber free of smoke via overpressure and thus to evacuate persons safely via the building core.
Complexity of the construction
Building a skyscraper is relatively simple, because the storeys often differ only slightly in their floor plan. Of course, when planning the technical building systems, you have to calculate exactly that water also has to be available on the 30th floor and that the lifts will bring the people to their destination comfortably and quickly. Compared to some areas of Asia and America, we do not live in an area of extreme seismic activity, so that only a manageable effort is required to secure the buildings accordingly.
Nevertheless, for a high-rise project, precise planning and precise site organization are required. This is due to the location, because often there is no storage space in cramped inner cities. The building material must be lifted directly from the truck with a crane where it is installed. In addition – in contrast to “normal” buildings – many tasks take place simultaneously. For example, while prefabricated concrete parts for shell construction are still being installed on the upper storeys, the facade is already “growing” up the lower storeys. Inside the building, the first preparations for the technical building systems are made.
It takes experts in planning and implementation, who prepare this logistical challenge with the high level of experience and organization required to coordinate hundreds of construction workers from the most diverse building trades in the smallest of spaces.
Modern tools achieve optimization
Innovative startup founders have meanwhile taken notice of this challenge and are seeking new solutions. For example, the Berlin-based company Sablono has developed a software with which all processes can be mapped and agilely managed. Others rely on the traditional use of lean management technology to optimize the construction process. This method is particularly suitable for high-rise construction, because it has a high repetition factor. In addition, most processes basically follow the same logic and allow the participants to optimize the process.
Certainly, the trend towards skyscrapers will continue in the next few years. The potential for area densification is too large and the migration into cities is too strong for it to be otherwise. It is likely we will see ever more bold concepts in the coming years. A rooftop pool could soon become standard and we can look forward to new and exciting ideas from the planners and project developers – and that will certainly bring new construction challenges.
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By Stefan Stenzel, Manager Development Monitoring at Cushman & Wakefield
Stefan Stenzel is Manager for Development Monitoring at Cushman & Wakefield in Munich and board member of BauMonitoring e.V., an association dedicated to the introduction of standards and training in monitoring.