Saturday, March 6th, 2021
Projects in Berlin and Hamburg
Warning, concrete – now there are wooden skyscrapers
From Kevin Schulte
Wood is more sustainable than concrete, which is why it is considered the building material of the future. In Berlin and Hamburg, high-rise buildings will even be built from the popular raw material in the coming years. But the construction method is more difficult to plan and significantly more expensive.
Almost every fifth new building in Germany is made of wood. The construction method is becoming more and more popular in this country. From 2007 on, the number of newly built wooden houses has increased every year. In 2019 it was over 22,000 in one year for the first time. But there, where construction is going on high, wooden houses are still few and far between: very few were built in 2019 in the city-states of Bremen, Hamburg and Berlin. UTB Projektmanagement now wants to prove that wood and big cities do not have to be mutually exclusive. The company is responsible for building the tallest wooden house in Germany. The "Woho" is to be built in Berlin-Kreuzberg: 98 meters high, 60 percent living space.
"It is an outstanding task to build in wood. Also horizontally. But we have appropriated this material," says UTB managing director Thomas Bestgen in the ntv podcast "Another learned thing" and looks back: "It was six years ago Years ago we bought a plot of land in Weimar and built it in wood for the first time. We have developed a large apartment building, only the access core is made of concrete. "
"Were absolutely exotic"
The UTB company has learned from its experience in Weimar. The "Woho" will be built in hybrid construction. That is, the cores of the house and the basement will be poured from concrete, the rest of the construction will be made of wood. Completion is expected in 2026 at the earliest.
A similar project wants that Real estate company Garbe in Hamburg. The "Roots" high-rise in HafenCity will also be constructed using wood. The building is to be 65 meters high. Construction started in November of last year and completion is planned for 2024. "When we started developing this wood project five years ago, we were absolutely exotic. At that time, wood construction was more in the single-family house area, but not in multi-storey residential construction," says Garbe boss Fabian von Köppen at "something learned again ". "Now everyone is talking about timber construction, also because of Fridays for Future. I am sure that the trend will gain momentum."
Wood has many advantages. The building material is relatively light and easy to work with. This saves time and it is significantly quieter on the construction site compared to conventional construction projects. There is also the aspect of sustainability. "Just three or four years ago, our customers were primarily concerned with saving energy. That has always been a big topic because it has to do with money. We are now noticing that people are increasingly seeing that they are living more sustainably. This trend is spilling over also about living ", says real estate entrepreneur von Köppen.
Complex planning costs
"All of a sudden, people ask: What do I actually live in? Is that strange gas? Is that ecological? The younger our customers are, the more likely they are to ask about it," says von Köppen, who hopes that "we are pioneers for one Turn in residential construction towards more ecology and climate neutrality. "
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But the plus in sustainability has its price. A wooden skyscraper is around twelve percent more expensive than a concrete model. This is mainly due to the complex planning. "For many topics, approvals have to be obtained on a case-by-case basis. That is always expensive. And even if we comply with standards one hundred percent or even exceed them, the responsible authorities may also demand what are known as fear surcharges The authorities discussed intensively whether the escape staircases could also be made of solid wood instead of reinforced concrete. "Ultimately, the building authorities decided on concrete staircases, although concrete has significantly worse properties than a wooden structure in the event of a fire," criticized Garbe boss von Köppen.
"A thick block of wood does not burn"
When it burns, wood will char and insulate the heat. The wood core protects itself to a certain extent and thus retains its load-bearing capacity. Steel and concrete, on the other hand, cannot withstand heat that long. Fabian von Köppen therefore wants the authorities to be more flexible. Wooden structures are at least as safe as conventional ones. "Everyone knows that a match is burning, but not a thick block of wood. There cannot be a fire like the one in London because here the wood is not packed with combustible materials."
In the fire disaster in Grenfell Tower in London, 72 people were killed three and a half years ago. The relatively easily combustible Styrofoam facade was one of the reasons why the fire was able to spread so much.
Just cut out and replace
This cannot happen in the planned wooden skyscrapers in Berlin and Hamburg, UTB boss Bestgen also makes it clear. "Inside we have no problem anyway. We have digital warning systems that are state-of-the-art. And we can work with spray mist systems or with real sprinkler systems."
Submerging the house would not mean a total write-off either, although wood and moisture are known to not go well together. "In Weimar we have just had water damage, so the house didn't break down. The nice thing about wood is that if you need to, you can cut out a swollen piece and replace it."
Are there any disadvantages? Yes, even apart from the lengthy planning phases and high fire protection requirements. In contrast to concrete, wood has natural enemies: for example woodworms or molds. And if at some point more wood is built in than can grow back, the world has a problem. The pictures of huge clearings of the Amazon are well known. In the "Roots" in Hamburg, for example, only 5500 cubic meters of wood are used. This amount of wood grows back in Germany within 23 minutes.