Cork is a material that you would usually expect to see inside a house – probably on the floor. This is what makes the cork façade and roof of the "corkscrew house" in Berlin's Staaken all the more striking. In visual contrast to this – and as a nod to the buildings typical of the region – the building shell on the lower floor has been clad in compressed concrete. This material has an open-pore, structured surface which makes the building base appear to have been dug out from the ground.

The materials chosen by the architectural firm of rundzwei Architekten are not the only feature that makes this home special. The division of the building levels is anything but standard. This is for good reason as the building regulations only permitted one full-height storey on the plot. By lowering the base of the building and using it as a living space, combined with the staggering of the areas on the upper floor, the architects maximised the total floor space to 320 m².

Above the base, the house is made from a timber construction. The façades and roof are completely clad in cork. The cork used comes from Portugal, where the cork granulate is a by-product of bottle cork production. It is pressed into façade panels under high pressure and heat, which pulls out the resin in the cork and binds the granulate. This means that the panels are naturally resistant to weather and mould, with no need for chemical additives. Furthermore, this natural product has very good insulation values. To improve energy efficiency even further, triple glazing with a Ug value of 0.6 W/(m²K) was used exclusively. The building was designed and constructed as a KfW efficiency house 55.

The rooms on the upper floors of the house are reached by means of the central, atrium-like staircase. These rooms can also be used flexibly, for example as additional studio apartments. The ground floor includes the levels for the living room and kitchen, as well as sleeping quarters with direct access to the pool outside. The lowest living space in the house is mostly below ground level. This, in combination with the compressed concrete walls, makes the space feel like a cosy den. By contrast, large glazed areas on the ground floor bring lots of light into the interior.

In order to make this structurally possible, clever lateral thinking was required. Circular supports were fixed to all corners of the building by means of their top and bottom end fixings, thereby securing the structure against sinking. This meant that the mullion/transom construction had to cover the supports both at the top and base point. "The challenge for us as fabricators was to fabricate the sections precisely and ensure that the all-glass corners were possible," explains Hans Timm from Hans Timm Fensterbau GmbH & Co. KG. He adds, "The installation sequence for the mullions was chosen to allow the fixing feet under the transoms to be completely concealed."

The Schüco FWS façade system with 50 mm face width was therefore used here. The mullion/transom façade features a wide selection of pressure plates and façade cover caps. The system can also be combined with Schüco window, door and sliding systems. The corkscrew house was enhanced with TipTronic windows and integrated bi-fold and lift-and-slide doors. Interestingly, the structural requirements for the lift-and-slide doors were met by the internal and external structural pilasters in the system.

Source: Profile magazine, issue 25