This project presentation was created in cooperation with BAUMEISTER.

Text by Falk Jaeger

Otto Steidle showed the way in the 1970s: housing construction as system construction. Now the architects of FAR frohn & rojas have tried something very similar in Berlin-Moabit and designed a residential building that is visibly composed of precast concrete elements. Our author has visited the building and explains the advantages and disadvantages of the concept.

Minimising costs in overpriced residential construction? Marc Frohn had enough ideas, but in order to try them out, he needed a suitable property. After years of systematic searching, the partner of FAR frohn & rojas found what he was looking for in Moabit, and he even managed to acquire the property: a typical Berlin residential area, built around 1895, but with defects, because the intersection of Waldenser/Emdener Straße had been bombed away during the war. One of the corners has remained undeveloped since then. Two streets and the courtyard, three free sides, proved to be ideal for Frohn's project, because he wanted to reduce costs through prefabrication. He had the logic of industrial halls in mind, stacked six times on top of each other.

Industrial building for living

The system is quickly explained: prefabricated columns and beams on the long sides, prestressed π panels that span 13.5 meters over the entire depth of the house, the fire wall on the one hand and a monolithic staircase with elevator on the other as fixed points. The undivided areas allowed individual drywall floor plans for the office ground floor and the ten apartments above. The gable-side axis remained cold. It accommodates the loggias, the elevator tower and Ada's open staircase.

The outer skin placed in front of the construction on the long sides is a standard curtain wall with floor-to-ceiling sliding windows, which is also available. Only twelve insulated baskets were required as special elements for the consoles on the loggias, where the cold beams connect to the warm supporting structure. Since excavating the pre-war foundations would have been too expensive, there is no basement. That's why the house stands on bored piles.

If you want to take advantage of the economic advantages of precast concrete construction, there are now efficient companies that emerged from GDR prefabricated buildings. Costs can be minimized in particular if you agree to their specifications. In this case, the circuit tables for the industrial hall system with the prestressed π plates already existed. However, the plates were too wide for Frohn's application.

Adjusting the axial dimensions and converting the formwork would have cost 40,000 euros. For example, wooden boundaries were set to shorten the edge width. If the π panels now collide, different distances are created between the webs – a circumstance that can be easily compensated for in the support system. Since the components weigh up to ten tons, a mobile crane was ordered for assembly, which erected the structure in six weeks. The time was determined above all by the six-centimetre-thick concrete layer to be applied to the π slabs, which had to harden over the weekend.

Source: BM 02/2020 - Prefabrication
Pictures: David von Becker

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