HIGHLIGHTS OF THE FRANKFURT SKYLINE
In recent decades, HOCHTIEF has constructed many high-rises in this financial metropolis, and it’s now working on number 26. Here’s a selection of the most striking and beautiful skyscrapers along the Main River.
At the very top, on floors 30 to 37, the lights are already on. The 17-meter-high entrance hall, one of the most imposing in Frankfurt, is also occupied. But no one has yet moved into the Marienturm, which rises to 155 meters. It’s “a special time,” says Manfred Wendig, the project manager of this high-rise, the 25th that HOCHTIEF has built in Germany’s banking metropolis. “This is still partly a construction site, but the first tenants move in next week.”Wendig adds that such transitional stages are normal for projects like this one and can even last for a while. That’s why his site office will probably continue operating with a reduced staff for about one and a half years after the building has been completed. “It takes time for a high-rise to be fully rented out. As a rule, rentals begin at the top and continue downward,” he explains. Because the tenants have their own ideas about how the floors they occupy should look, help from HOCHTIEF is also needed in the phase of tenant-specific improvements.
Wendig, a native of Brandenburg, came to Frankfurt in 1990 after receiving his engineering degree from TU Dresden in eastern Germany. Frankfurt may be Germany’s most “western” metropolis. Here money reigns supreme—a bold message that’s symbolized by the glittering towers of major banks soaring into the heavens. The Marienturm’s main tenant, occupying the top eight floors, is the gigantic U.S. investment bank Goldman Sachs. On account of a possible Brexit, Goldman Sachs is moving its European headquarters from London to Frankfurt.The bank’s German team was previously housed in another HOCHTIEF building, the 257-meter-high Messeturm or Trade Fair Tower. The team will now be expanded to 700 members and will soon move into the Marienturm. On the top floors, where the lights are already on, experts are already testing the computer technology that will connect the financial experts with the global data stream. The top managers will be the last ones to move in—into the spectacular corner offices at the very top, of course. There the Spanish star designer Patricia Urquiola has created an airy lounge-like atmosphere for the top bankers.
A DYNAMICALLY GROWING SKYLINE
Wendig, who lives with his family in the nearby Taunus mountains, has watched Frankfurt grow for almost 30 years. And he has played an active role in this growth. His first major project for HOCHTIEF was the Commerzbank Tower, a 259-meter-high building designed by Lord Norman Foster that still dominates the skyline. It was followed by more Frankfurt landmarks. In 2017, Wendig and his team completed the 66-meter-high Praedium, an exclusive residential tower that testifies to a trend previously considered impossible in Germany: the belief that it’s chic to live in a high-rise building in a city center. Skyscrapers have always been accepted in Frankfurt, in spite of the critics mocking “Krankfurt” and “Bankfurt.” Today it’s not only the citizens of Frankfurt who are proud of their skyscrapers. Artists, the cultural scene, and creative urban developers all praise the dynamically growing skyline, at least partly thanks to the high-quality architecture.
» IT OFTEN MAKES MORE SENSE TO CONSTRUCT A LOWER BUILDING. «
MANFRED WENDIG, PROJECT MANAGER
“It’s not easy to get a construction permit for a high-rise in Frankfurt,” says Wendig. In other cities, the designs are taller and more spectacular. In Moscow, for example, high-rises are seldom lower than 300 meters. In Asia and the Middle East, “every building has to be a real eye-catcher—a clearly visible prestige project.” By contrast, in Frankfurt the builders prefer harmonious high-quality design, well-functioning ensembles of high-rises, and top-quality workmanship. Over a dozen new high-rises are currently under construction, even though suitable inner-city sites are rare. In Germany, you can’t simply build a high-rise in whatever way you like. Potential neighbors and municipal governments provide input in a detailed “tower block skeleton plan.” The criteria include not only height, aesthetics, and construction quality but also shading, wind streams, and fresh-air corridors. These high hurdles have helped to ensure that Frankfurt’s skyscraper culture has remained fairly “down to earth” in comparison with those in other countries.
HIGH-RISES BUILT ON PILES
“The strengths of the Frankfurt projects are their rather sober but timeless designs and their economic efficiency,” says Wendig. “It often makes more sense to construct a somewhat lower building.” To understand that, we must keep in mind that the ratio of a skyscraper’s total floor space to its useful floor space actually makes it an inefficient building. It would be cheaper to build a wide and low building on a greenfield site. One reason for that is difficulty of digging the foundations of a gigantic high-rise. The rule of thumb is that around one per three years of construction time is needed for the foundation. Wendig recalls that when the Commerzbank Tower was built, more than 50 cylinders, each one between 40 and 50 meters long, had to be bored into the building ground. Because the machines needed for this task were gigantic, only three piles could be worked on at a time in the foundation pit. That takes time. The piles for the smaller Marienturm only had to be bored between 25 and 30 meters into Frankfurt’s relatively soft clay, which is not very suitable for high-rise construction. Excessive subsidence can be avoided only through the intricate interaction of the piles with the 3.4-meter-thick high-rise foundation slab, as well as ingenious foundation engineering. This is much easier in New York City, where everything stands directly on the bedrock, Wendig adds.
OVER 80 PERCENT OF USEFUL SPACE IS A LOT
Building high-rises is complicated, not only because of the subsurface conditions. The higher a skyscraper is, the stronger its core has to be in order to ensure solid statics. And the higher it is, the more elevators, stairways, and shafts for supply technology it needs. The magic formula for a high-rise’s economic efficiency is hidden in the cross-section of an individual floor. Lots of “core” means less rentable floor space. The Marienturm has over 80 percent of useful floor space—a very good ratio of rentable to total floor space. This represents considerable progress compared to older high-rises.
In the years ahead, new elevator systems could enable high-rise construction to make a huge leap forward in efficiency. In the near future, the market may be transformed by systems that enable several passenger cabins to use the same shaft. Designers are also tinkering with modern circulation systems that could operate like contemporary versions of the good old paternoster lift. High-rise construction will continue to be exciting in the future.
When Manfred Wendig strolls through Frankfurt in his free time, he can tell his family stories about urban development as well as his personal history. “Look at what your dad helped to build” is a sentence he repeats with pride. “Everyone can see a high-rise,” he says. “There’s a lot of talk about them. They aren’t hidden buildings. You don’t have to look for them or explain their location to anyone.” This may be the reason why skyscrapers are so fascinating. Every new high-rise in Frankfurt clearly shows us that the world, and our daily lives, have moved a little bit ahead—and that usually makes us feel good. People like to see high-flying ambition. And in pulsating, increasingly popular Frankfurt, this atmosphere becomes palpable.