In 1959, Aronsohn designed the structure of the original Van Ommeren office buildings. Among other reasons, the fusion between Van Ommeren and Vopak necessitated upgrading the buildings.
The high-rise construction was partially designated for rental residences and office space. For the building’s exploitation, it was desirable to enlarge the existing office space by making the building taller.

Project information


Building structures




Maarsen Bouw en Ontwikkeling (MBO) / Westerlaan CV


Ector Hoogstad architecten Rotterdam

Project size

High-rise office: approx. 17.000m2 GFA renovation, 6.500m2 GFA new construction on top of original construction

Start of project




Consulting services

Analysing existing structure with regards to reusability, determining structural resources for enlarging high-rise construction, structural design and engineering of renovation and new construction
chevron-right chevron-left

Concerning the high-rise construction, Aronsohn has researched if and how the enlargement were possible. To this end, the capacity of the concrete structures and foundations have been extensively analysed on the basis of modern insights. Additionally, maintaining the then-present structures has been economically weighed against demolishing the structures and constructing new ones. After extensive calculations and determining the foundation’s maximum load capacity, it was found that the tower could be enlarged to up to 76m, up from the original 60,5m. This would require reinforcing the stability core and foundation slab, among others.

Because of the building’s greater height, moments increase in the existing concrete core to the point that the core can no longer hold. The moment on the foundation’s level has to be absorbed by the piles directly underneath the core. In the process, the piles are overloaded. So leaving the core unchanged would cause significantly large bendings. The solution was found in an outrigger structure. This involves the circle of columns around the core with the stability. Additionally, in order to further spread moments in the foundation, extra concrete walls have been added to the basement.