On the corner of Beethovenstraat and Strawinskylaan, they are working hard on the extension to the WTC that has been given the name Tower Ten. The Amsterdam WTC complex has existed since the 1980s. In those days, the idea that Zuidas would ultimately grow to become Amsterdam’s financial centre was still a distant dream. But the development of Zuidas continued. As the years progressed, various parts of Amsterdam WTC were updated. In 2018, its owner CBRE Dutch Office Fund decided to realise Tower Ten. This involves the existing WTC Amsterdam being increased in height and extended with the addition of three new pavilions on Strawinskylaan. Planning engineer for contractor Ballast Nedam, Hans van der Liet, escorts us through an inconspicuous door in the corner of the office section into the huge construction site.
Better to use saws
This minimal separation immediately reveals why construction work is so difficult here. Van der Liet: ‘This kind of extension to a building with so many offices is complicated because the work also involves noise.’ The nuisance that this would cause to Amsterdam WTC tenants needed to be limited as far as possible. ‘That meant that we had to adapt the construction methods. Where previously we’d been chopping away the old concrete, we soon decided to use saws. It’s much less noisy. We also announced any unavoidable disruptive work well in advance, ensuring that tenants were prepared for it. Although there’s still room for improvement, we’re heading in the right direction.’
This is good news, because there is still a lot of work to be done. ‘Not only do we plan to add another ten floors to the building on Beethovenstraat, we also intend to extend it on Strawinskylaan with three new pavilions beneath an undulating roof’, explains Van der Liet. ‘In order to make this possible, we had to start making modifications to the existing foundations from the outset. Obviously, it wasn’t designed to take the weight of ten extra floors.’ Van der Liet admits that the job is challenging. ‘From the existing underground car park, we created extra load-bearing capacity by adding new foundation piles. Of course, because an underground car park is not particularly tall, the foundation piles were delivered in small sections that we screwed together on site and inserted into the ground using a small pile-driving machine.’ This ultimately resulted in an additional 332 foundation piles around 25 metres into the ground, after which the car park was immediately extended.
Extending the width of the WTC proved to be a difficult job because the original concrete structure to which the pavilions will be attached needed to be preserved. Van der Liet: ‘These days, you need much more space for installations because they’ve become more advanced and you also want to guarantee effective climate control. Because you’re working within an existing concrete framework with a set floor height, you have to apply some ingenuity to create more space. In the end, we replaced the original thick concrete floors with relatively thin concrete floors supported by steel girders. These girders have holes in them where some of the installations can be hidden. This ensures there is sufficient space for the installations without drastically reducing the height of each floor.’
Onwards and upwards
Work is continuing on the three new pavilions on Strawinskylaan. At street level, Van der Liet shows us how far the three buildings will reach. ‘There’s quite a lot still to be added.’ This construction process will be done rapidly. ‘New-build is easier to realise than renovation or the reinforcement of an existing structure.’ Some of the new tower at the front can also already be seen. This is being built onto the existing section. ‘We’ve almost reached the height of the existing building. In the middle, you can see the core, the heart of the tower. Here, there will soon be lifts, staircases and installation shafts.’ In early 2021, the new-build section will begin to rise above the existing building. The whole tower will also be given a modern glass façade and various roof terraces will be landscaped. ‘The new section of Amsterdam WTC is scheduled for completion in mid-2022.’
When this major extension has been completed, the footpath on Strawinskylaan will be lengthened. The result will be a continuous footpath along the whole of Strawinskylaan. Close to Tower Ten, there will be a staircase from this path leading to the footpath and cycle path on Beethovenstraat. The public space in that area will also be newly landscaped. However, this work will take some time before it is completed. It’s now time to leave the construction site via the secret door and return to the normal world of the WTC. Or maybe not – there’s not really any ‘normal WTC’ at the moment…