he project is a new 900m² retail outlet in the southern Swedish city of Jönköping. About a third of the floor area is used as a cafe with a drive-through facility serving workers around the area. The major part is rented by the ‘Royal Design’ group as a high-profile setting for its retail store concept, offering around 100,000 products for the home, including furniture, lighting, decoration and interior design.
Golden copper alloy
Such a building had to exude quality, not just in its conceptual design but also its materials and detailing, and the extensive use of Nordic Royal – an innovative golden copper alloy from Aurubis – as an external skin certainly met this demand. The word ‘royal’ itself is historically associated with copper alloys such as bronze, as well as gold, and this was an influence. But, at the same time, sustainability, recycling capability, environmental impact and long-life properties were also important to the final material decision.
Within its edge-of-town shopping centre location, the Royal Design store stands insular but is surrounded by many larger and taller buildings. The design concept prioritises form and visual impact, intentionally with a powerful and contrasting response to its surroundings.
Because of the central location of the building, the key consideration was that all sides of the scheme matter: walking around the building will reveal different architectural experiences, ranging from abstract rectilinear facade compositions to complex architectural forms.
The built project is very different to the early concept sketches but the whole design process proved essential in delivering the right solution. The final plan form combines three interconnected rectangular zones, each highlighted by a different roof form – but only revealed from the main entrance frontage. Two zones provide completely flexible retail space, whilst the third – signalled by its higher roofline – houses the cafe and services.
The main entrance facade is open with extensive glazing framed in black and following the building form’s acute angles. The side elevations are calmer but still exciting with irregular windows, continuing the black-edged theme that also oulines the complex geometry of the building.
Exclusive architectural material
From the start, the client wanted to achieve a knife-sharp entrance facade and then harmonise the other facades with the surroundings but still make the building look unified. All the facades and sloping roofs are therefore clad in Nordic Royal golden copper alloy from Aurubis, formed into cassettes with hidden fixings. This addresses the client’s requirement for the complex shapes to be covered in an exclusive and reflective metallic architectural material exuding quality.
Beyond the architectural concepts, there were also technical and structural challenges with detailing and developing the design. Here, both architects and structural engineers had to work together outside their comfort zones to create the essential distinct, clearly defined shapes and clean facades. Particular care was taken with detailing the external skin so that the complex corners and different angles always connect elegantly. While appearing effortless, these were actually particularly demanding. There were also special solutions to technical issues such as drainage, with rainwater conveyed in hidden gutters, covered and fully integrated with the roof, and then to downpipes hidden within the Nordic Royal facades.
Nordic copper and alloys
Nordic Royal is an alloy of copper with aluminium and zinc, giving it a rich golden through-colour and making it very stable. It has a thin protective oxide layer containing all three alloy elements when produced. As a result, the surface retains its golden colour and simply loses some of its sheen over time, as the oxide layer thickens with exposure to the atmosphere to give a matt finish. Unlike most copper alloys and surfaces, it does not develop a blue or green patina. As well as exuding a sense of visual richness and quality, the golden alloy offers outstanding mechanical abrasion resistance, extremely high corrosion resistance and durability as well as excellent stability and material rigidity. The material can be easily cold-shaped and processed using standard techniques.
Nordic Royal is produced by Aurubis, part of the world’s leading integrated copper group and largest copper recycler. Other traditional copper alloys include Nordic Brass. Initially with a distinctive golden-yellow colour, when exposed to the atmosphere, the surface begins to darken within weeks and can change to a dark brown in around a year. The latest addition to the range is a pre-weathered surface for Nordic Brass. Other alloys include Nordic Bronze, initially with a similar colour to standard copper. When exposed to the atmosphere, the surface gradually changes to a stable, dark chocolate brown.
Copper is one of our oldest building materials with unique properties. Its surface finishes develop naturally over time, unlike other materials that aim to copy them. The Aurubis Architectural range provides straightaway surfaces that otherwise would take years to develop in the atmosphere – particularly on vertical facades. The processes involved are generally similar to those taking place over time in the open, utilising copper mineral compounds, not alien chemical processes.
Essentially, they bring forward environmental changes without taking away the integrity of copper as a natural, living material. All these surfaces form an integral part of the copper, generally continuing to change over time, and are not lifeless coatings or paint. The material is easily bent and formed and there are no limitations on the length of copper sheet or strip because whole coils are treated on the production line, not just limited size sheets.
Nordic Blue, Green and Turquoise ranges have been developed with properties and colours based on the same brochantite mineralogy found in natural patinas all over the world. As well as the solid patina colours, ‘living’ surfaces are also available with other intensities of patina flecks revealing some of the dark oxidised background material. The Aurubis Architectural range also includes Nordic Standard ‘mill finish’ and Nordic Brown pre-oxidised copper, offering lighter or darker shades of brown determined by the thickness of the oxide layer.