Stretching the Chewing Gum Factory to an Office Building

Transforming a Former Warehouse in Amsterdam

// The Amstelkwartier district in southeast Amsterdam was long dominated by industry. Following the gradual closure of the Zuidergasfabriek in the 1970s, the district has now been converted into a modern residential and office district. The site of the KBF chewing gum factory, directly adjacent to the south, also represents an important building block in this development. The company was founded in 1948 shortly after the Second World War and had been operating on Paul van Vlissingenstraat in the Amstelkwartier since 1956. The two founders explicitly intended the company name "Maple Leaf" to be understood as a tribute to the Canadians, whose soldiers played a key role in the liberation of the city in 1945.

After production ceased in 2003, the existing buildings from the 1950s, 1960s, and 1980s initially stood empty for several years. Following a change of ownership in 2007, the site has since developed into a vibrant working environment and has been given a completely new look through various renovations and new construction projects. The 65-meter-high "Postillion" hotel tower, completed in 2018 according to plans by concrete, serves as a prominent eye-catcher. A residential building with 100 units is also scheduled for completion in the coming years.

A Reimagined Warehouse

NEXT architects, based in the area, has been instrumental in the site’s regeneration. As one of the first tenants, the firm soon became involved in the district’s urban planning. Most recently, the architects also fundamentally transformed the dark red clinker-clad warehouse of the former chewing gum factory and converted it into a modern office building.

The former production hall of the Amsterdam Chewing Gum Factory (KBF), which was closed down in 2003, now brings together past, present, and future.

As part of the conversion and extension, the single-story shed-roof building was generously opened up and, to the east, a four-story new building constructed using modular steel construction and featuring large-format glass facades was added. To the southwest, the building is complemented by a similarly designed six-story new building, and in the centre of the site, the planners also added a six-story timber staircase. The design is completed by a single-story existing building to the southeast, which now houses a modern restaurant in place of the former company canteen. The interplay of the various buildings creates a contrasting ensemble that successfully contrasts with the other new and existing buildings on site.

"To emphasise the relationship between old and new, the balcony overhangs were given the same angle as the shed roofs below."

Marijn Schenk, Project Architect and Partner at NEXT architects

A special feature of the design are the angularly projecting and recessed glass fronts and balconies of the two transparent office buildings, which surprisingly reflect the existing sawtooth roof structure of the old building: "To emphasize the connection between old and new, we simply folded the sawtooth roof of the old building upwards by 90 degrees, thus arranging it vertically instead of horizontally," explains Marijn Schenk, project architect and partner at NEXT architects. "As a result, the cantilevers of the balconies have the same angle as the sawtooth roofs below." The undersides of the balconies and all interior ceilings are alternatively clad with wood panels, and the facades and all roof surfaces have been lushly planted with greenery. The new building's interior is similarly modern, with the various building volumes integrating to create approximately 8,400 square meters of flexible office space. All areas are accessed and connected by the centrally located staircase with its pleasant, natural wood look.

A Focus on Sustainability

With the transformation of the former warehouse, the conversion of the former KBF chewing gum factory has taken another important step forward: "As early as 2012, we were thinking about how we could transform this area from an industrial zone with large warehouses into a dynamic residential and work district," Marijn Schenk recalls. "From the very beginning, we placed great emphasis on preserving the site's existing strengths and combining them with modern new buildings." High sustainability standards also played a key role in the concept from the very beginning. In the implementation of the KBF warehouse, this requirement was met, among other things, through the diverse use of the various roof surfaces. To enable optimised rainwater management at the site, retention elements were integrated into all areas. Directly above, sedum mats were laid and a 420 m2 photovoltaic system was installed.

Complex Roof Structure

As part of the implementation, a 3mm thick bitumen backed vapour barrier was first applied to all roof surfaces. The employees of the contracted company Daktec BV from Kampen installed an FM-approved PIR insulation board directly over it. The self-adhesive EPDM waterproofing membrane RESITRIX® SK W Full Bond from CARLISLE® was used as the top layer. This root-resistant membrane contains no plasticisers and is completely environmentally friendly. In addition, the membranes offer a service life of over 70 years due to their extremely weather- and aging-resistant properties.

In the next step, retention elements with a height of 85 mm were applied over the RESITRIX® SK W Full Bond waterproofing and a protective membrane over a total area of 620 m², thus achieving a water storage capacity of up to 80 liters per m². As a result, accumulating rainwater is drained away with a time delay, preventing the local sewer system from becoming overloaded and significantly reducing the risk of flooding at the site. A special substrate was applied as the upper layer above the retention layer, followed by a green roof made of sedum, creating an attractive "fifth facade" for the on-site employees in the adjacent offices. The green roofs have a positive impact on the microclimate and biodiversity at the site, and they also enable optimised insulation and cooling in the interior. The retention elements underneath ensure that the greenery is sufficiently moistened with rainwater even during prolonged droughts.

The retention roof drains rainwater into the local sewer system with a time delay, preventing it from becoming overloaded.

Finally, the photovoltaic system was installed. Alternatively, a 198 m2 roof terrace was created on part of the retention elements, using 50 x 50 x 5 cm thick slabs. The edges of the roof surfaces were designed as vegetation-free zones with gravel.

In addition, the planners implemented an attractive green facade, integrating special planters on the balconies and vertical wire rope trellises along the facade. The result is an airy green structure that completely preserves the transparency of the glass facade.

Robert Uhde

Project: KBF Warehouse

Location: Daniel Goedkoopstraat 14, 1096 BK Amsterdam

Client: Tristan Capital Partners, London

Project Developer: NEOO, Amsterdam

Design: NEXT architects, Amsterdam

Construction Contractor: Heilijgers, Amsterdam

Roofing Contractor: Daktec BV, Kampen