'Construction cycle of 10 days per floor is sacred'

DESA is currently working on the execution of the complete concrete work, supplying and assembling the support for the cast-in-place floors and wall formwork systems, pouring the concrete, and supplying and installing the reinforcing steel for basement and high-rise buildings. 

Most of the structural work will be carried out by DESA from the foundation. The construction site at Barajasweg in Amsterdam Sloterdijk is not easy to access. Just-in-time work is required on slender towers, and the shell is largely poured on site. "Quality and execution reliability are everything," says execution manager Gert Visser. "VERTICAL is a customized project. Each floor requires intensive cooperation, for example with the installers. It is important that we can run as many right 'trains' as possible for progress."

For DESA, this is daily business, Visser continues. "We are active in non-residential construction, utilitarian housing construction, petrochemical industry and civil sector, among others, and are also building the similar Trudo Tower in Eindhoven." DESA is executing the project with its own superintendents, laborers, technical office team and custom fabricators. "In order not to impede logistical progress and to be able to deploy personnel optimally, we sometimes work through on Saturdays and, for example, the Friday after Ascension Day. A project like this is an international undertaking and then you have to keep going when you can."

'Per floor, intensive cooperation is needed'

Green balconies

The total project duration for the concrete work is approximately 18 months from foundation to roof, and the construction cycle for each floor of the tower is 10 days. Almost nothing is repetitive about VERTICAL's shell; with various floor heights and staggered loggias, it remains a challenge to stay in the cycle with all parties. Visser: "Each floor has about 1,100 m² of floor space up to the fifth floor. From the sixth floor on, each floor has 700 m² of cast in situ concrete floor area and prefabricated 'flower boxes' are poured along by iso baskets." The total area of these "green balconies" is about 150 m² on each floor. DESA installs 22,000 m² of floor support with the drop head system. Compared to regular steel floor props, this aluminum underpinning has a significantly higher load capacity and low dead weight. This makes the supports easier to assemble and disassemble, which improves construction speed. Furthermore, DESA places 18,500 m² of formwork for foundations, walls and columns by supplying its own formwork material and engineering services. In addition, DESA is supplying and installing the 1,400 tons of reinforcement and 8 tons of steel structure for the project. In week 23, façade closure began, starting with the sixth floor, followed by building levels -1 through 5. "Obviously in good cooperation with main contractor Heijmans," Visser concludes.