Formerly a chewing gum factory, now a flexible office building: the project by NEXT architects shows how existing buildings can be repurposed in a sustainable way.

BLACKPRINT: Mr. Schenk, how did the idea come about to convert the former warehouse of the chewing-gum factory in Amsterdam into a modern office building?

Marijn Schenk: I need to give some background: The KBF site was built in the 1950s as a production facility for the "Maple Leaf" brand. At the time, chewing gum was regarded as a symbol of freedom — the Dutch had just come to know it through the Canadian liberators. Between the 1950s and the 1980s the site was expanded in several stages. Around the year 2000 the complex stood empty because production had been moved to the edge of the city. A few years later it was purchased by the investment company Lingotto with the idea of creating a place for creative businesses. That was in 2007, and we at NEXT architects were among the first tenants on site. Back then it looked very different: the surroundings were industrial, old delivery vans and scrapped cars were everywhere. In the evenings the area felt quite deserted — there were only a few clubs and a rave venue.

BLACKPRINT: The area’s image has changed considerably since then...

Marijn Schenk: Yes, indeed! In 2019 the site was sold to today’s owners, Tristan Capital Partners and Timeless Investments. Together we then had the idea of further developing the area, increasing density, and creating a mixed neighborhood for work and living.

BLACKPRINT: As a first step, the old warehouse was converted and extended. How did you integrate the existing building architecturally and functionally into the new structures? And what role does the central timber stair core play?

Marijn Schenk: First we examined how the existing structure of the former chewing-gum factory could be used for densification and where there were potentials for further development. As a result, we proposed to the client to build two new wings of four and six storeys over the single-storey shed-roof wing of the former warehouse. Between the two wings we placed a central staircase made of wood. This arrangement allowed us to externalise the entire vertical circulation and thereby create a high degree of flexibility in how the spaces are used. Based on this study we were then commissioned to work out the first implementation phase.

: A bird's-eye view clearly shows the location of the former chewing gum factory in the neighbourhood.

BLACKPRINT: And how did the idea arise to vertically pick up the shed-roof form of the original industrial hall in the new façades?

Marijn Schenk: It was important to us not to simply build another ordinary office building but to create something that refers, in terms of design, to the industrial past while remaining architecturally distinctive. So we looked for a way to use the characteristic shed-roof structure of the existing building as a motif for the façades of the new volumes. We did not want to merely repeat the roof form; instead we rotated the characteristic angles by 90 degrees vertically so that angular, recessed and projecting outdoor spaces are formed in front of the office floors. This gives the building a sculptural quality that also recalls the industrial history of the site.

Caption: In designing the façade, the architects took up the characteristic sawtooth roof structure of the existing building and rotated it vertically by 90 degrees.

BLACKPRINT: The result is a striking building with an individual character. What role did material choice play in this context?

Marijn Schenk: To underline the industrial character, we deliberately used materials such as wood, steel and glass. The generous glazing provides bright, open floors with wide panoramic views. In contrast, the largely closed stair core constructed from wood is clad with translucent polycarbonate elements. These let daylight into the building interior but do not provide views. It is all the more surprising when you then enter the open office floors!

Material collage made of wood, steel, glass and translucent polycarbonate elements.

BLACKPRINT: Looking back: what was the greatest constructional challenge in converting the Amsterdam chewing-gum factory?

Marijn Schenk: To integrate the existing warehouse into our new building, it was necessary to strip the complex back to the façades. Only then could we construct a new, load-bearing foundation that meets the requirements of the enlarged building. Where additional storeys were not added, the original roof could be retained in full. The other roofs were temporarily dismantled and could only be reinstalled later.

BLACKPRINT: A central element of your design are the various green roofs. What role do these areas play with regard to sustainability?

Marijn Schenk: The increasing heating of our cities is a reality we must address. In our work we therefore specifically seek strategies to counteract this development. Green roofs can play an important role. In the transformation of the former chewing-gum factory we implemented a particularly species-rich vegetation layer with various sedum species and also integrated a retention layer that stores and delays the runoff of rainwater. As a result the microclimate on site is improved and the burden on the sewer system is reduced. The concept is completed by the installation of a photovoltaic system for sustainable energy generation.

The floor-to-ceiling glazing on the office floors offers sweeping views across the city.

BLACKPRINT: At the same time you also greened the façades...

Marijn Schenk: Yes, we wanted to set a soft, living component against the existing steel-and-glass architecture. Therefore we integrated vertically running wire-cable trellises around the building for plants to climb. Especially on the very sun-exposed south façade this vertical garden acts as a green buffer zone, providing extra shading and cooling. Inside the building the greenery also becomes a living connection to the outside world. Another element for implementing greater sustainability is the redesigned courtyard. Where cars used to be parked, we created a small urban park — conveniently right in front of our office. In good weather we can simply open the doors and have our lunch break in the green.

The greening of the façades emphasises the sustainable approach of the building.

BLACKPRINT: A beautiful example of how functional design, climate adaptation and quality of stay can work together. Back to the green roofs: why did you choose the EPDM waterproofing membrane RESITRIX® SK W Full Bond from CARLISLE® for the implementation?

Marijn Schenk: The RESITRIX® membrane provides reliable protection against moisture and root penetration and is ecologically harmless because it contains no plasticisers. In short, it offered exactly what we were looking for for this "green-blue" roof with vegetation and a retention layer. Added to that, the membranes have a very long service life of more than 70 years. That was very important to us, because replacing the membrane would require removing the entire green roof.

BLACKPRINT: With projects such as the Woensel-West quarter in Eindhoven or the Uilenstede campus in Amstelveen you have previously dealt intensively with the transformation of existing structures. What do the different projects have in common and what do you understand by a successful renovation or redesign?

Marijn Schenk: For us, a transformation is successful if you manage to reuse some of the existing qualities and if you succeed in giving the area a new character and a new meaning. A good example is the Uilenstede student campus from the 1970s, which was originally planned to be very introverted with hardly any places for encounters. As key measures we therefore created a number of openings and demolished some buildings to enable significantly more openness and visual connections. In addition we added a glazed pavilion as a place for meetings. In this way we were able to largely preserve the existing structure and, with a comparatively small intervention, radically change the function and atmosphere of the place.

In transforming the Woensel-West neighbourhood, the architects succeeded in creating a colourful redensification of a district dating from the 1930s.

During the transformation of the Uilenstede student campus in Amstelveen, the architects added a centrally located glass pavilion as a meeting place.

BLACKPRINT: NEXT employs around 55 people across the two locations Amsterdam and Beijing. Together you realise a wide range of projects — from housing to educational and cultural buildings to bridges. What do these different projects have in common and how would you characterise NEXT’s architectural approach?

Marijn Schenk: In our office we use the claim "NEXT Connects". For us this means we look for connections — between people, but also between places and between past and future. Even in our infrastructure projects it is about building bridges. Rather than following a fixed style, we pursue a context-driven approach: our architecture should enter into a relationship with its surroundings. This attitude is a central part of our work.

BLACKPRINT: And which projects are you currently working on?

Marijn Schenk: At present we are realising, among other things, the Cartesius primary school with daycare and sports hall in Utrecht. The design is based on the neighbourhood’s high demands for a healthy lifestyle and a healthy living environment — formulated within the underlying "Blue-Zone" concept. Against this background we developed the new building as an energy-neutral structure that also meets the urban requirement for circularity. The result is a spirally organised building with a planted inner courtyard that blends smoothly into the surroundings. By deliberately incorporating the surrounding landscape up to the roof gardens, an ensemble is created that takes up and continues the neighbourhood’s green character architecturally.

Visualisation of the Cartesius Primary School with daycare centre and sports hall in Utrecht.

BLACKPRINT: We are looking forward to the finished building and thank you for the interview!

The interview was conducted by Robert Uhde.