An impressive dark building has appeared over the winter in the Kista district of Stockholm. In accordance with the original assignment by real estate company Klövern, the building was constructed from concrete elements, but to fulfil the wishes of the end user, it is also almost completely black, creating a contrast with the adjacent white building that was constructed earlier.
The assignment was a challenge for the architects right from the start, as black pigment is considered by the concrete element industry to be one of the trickiest to work with in terms of achieving a consistent finish. At the same time the architects had to come up with a solution that satisfied all the wishes of the end user. Fortunately, Kristin Gausdal and Peter Walker from BAU Architects found a solution quite rapidly.
While exploring different options they came across Graphic Concrete, which appeared to meet the wishes of both the customer and the end user. Graphic Concrete would enable black pigment to be used safely, as the pattern would obscure variations in the tone, while the addition of black aggregate would create an even blacker impression than if pigment alone were used.
The next challenge was to convince the city’s architect that the black concrete surface would work and to gain approval from the customer for the additional expenses of using a graphic concrete pattern – which, of course, were only alternative costs compared to using other forms of surface treatment.
It was clear from the start that the pattern should not present an image but instead be used only to create depth and balance for the overall look of the façade. The architects ultimately selected Piksel negative, which can be found in Graphic Concrete’s GCCollection. However, Gausdal and Walker were keen to modify the pattern, as they wanted it to continue across the concrete seams without any dots being placed too close or too far from each other at the seams.
To realise their vision, they made full-scale prints of the elements and tested to see how the pattern would work on each element. They even hung the 1:1 prints from the window to term the optimal pixel size. Different concrete mixes were also tested to achieve the right degree of darkness and the optimal appearance.
Altogether the architects designed 55 unique elements to achieve an interrupted pattern. The elements also had different physical properties, which created its own challenge for the concrete element factory. In order to achieve a consistent result, the elements had to be washed at precisely the same time during the hardening process and in the exact same way.
Thanks to the architects’ thorough preparation work and relentless precision, the end result is certainly impressive and Gausdal and Walker are justifiably satisfied. Even with all the testing they did, the architects were positively surprised by graphic concrete.
“The way the sunlight hits the patterns on the façade creates entirely new dimensions. The surface shines splendidly during sunsets, and when it rains it becomes even darker,” Peter Walker describes.
Gausdal and Walker are in no doubt that they will use graphic concrete in future projects. They appreciate the limitless possibilities and diversity of the graphic concrete solution. At the same time they are well aware that success is the sum of many factors. The contractor has to understand what they are buying, the concrete element factory has to deliver consistently high quality, and the end user has to understand the character of concrete as a living construction material.
Location: Torshamnsgatan 23, Kista, Sweden
Architects: Byrån för Arkitektur och Urbanisme
Concrete element factory: Benders Byggsystem
Construction year: 2016
Product: Repeating pattern