The Terraced Tower gives Rotterdam skyline a new face

Following in the footsteps of the Montevideo (158 m), New Orleans (152 m) and Maastoren (165 m) towers on the Kop van Zuid, BESIX Nederland continues to build on Rotterdam's skyline. Indeed, in the fall of 2017, the multidisciplinary construction company began work on a 100-meter-high residential tower on the north side of the River Maas, commissioned by developer Provast. The Terraced Tower will house various types of modern urban apartments, including 258 rental and 86 owner-occupied units. The tower owes its name to the terraces along the full width of all residential units, with spectacular views of the city and Maas.

"The Terraced Tower was tendered as an Engineer & Build contract based on a Final Design," says Michel Mulder, Operations Manager at BESIX Nederland. "Using Royal HaskoningDHV's structural design as a foundation, our own engineering firm further elaborated the construction of the residential tower. In close collaboration with OZ Architects, we also provided the structural and aesthetic optimization of the building. In the fall of 2017, we started the demolition of the old office building on the site, including the existing foundation at level -1." The Terraced Tower will be realized in the primary flood barrier on the Boompjes, which holds back the high water of the Meuse River, he says. "Moreover, on the north side of the building lot is adjacent to the Hertekade, with the Scheepmakershaven behind it. That means we have to deal with water on both sides, which placed special demands on the foundation."

Complex interplay of forces

"We excavated the subgrade to a level of almost -3 stories," Mulder says. "Then we installed a new, thick foundation floor. We chose in-situ concrete with in-situ walls for the construction. The facade is constructed of wood-frame elements combined with aluminum window frames. Towards the top, the building becomes increasingly slender. However, the various floors protrude. In order to be able to absorb this interplay of forces, the pushing embankment from the Boompjes and the water on both sides, we used a cofferdam with a strut frame and anchors on several layers. Because a cable and pipeline strip runs right through the project that could not be disturbed, BESIX Nederland first poured a concrete slab. "Below that, we excavated the basement. In addition, we used the concrete slab to properly support the outrigger frame."

The facade will be constructed of wood frame elements combined with aluminum window frames.

Logistical challenges

In addition to the construction, the inner-city location also poses a challenge, Mulder emphasizes. Especially in terms of logistics. "We don't actually have a construction site. Moreover, the Boompjes is an important transit route to and from the city. In order not to disrupt traffic flows, we placed our tower cranes on two portals. Trucks supplying the construction can drive underneath." All deliveries take place just-in-time, he says. "The use of the tower cranes is also coordinated in close consultation. Definitely not a sinecure, with three construction streams and over 120 people on site today. Moreover, we are dealing with all the perils surrounding the corona virus. Fortunately, our construction partners have shown great flexibility and willingness to allow the construction to go ahead as unhindered as possible. For that, they deserve a big compliment."

Custom

Meanwhile, structural work has progressed to the 11th floor. Three layers below that, the facades will be installed, Mulder says. "We have also now started the finishing work." The rental apartments will be finished in accordance with the Program of Requirements of landlord CBRE Global Investors. "For the owner-occupied apartments, residents can choose their kitchen, plumbing, interior doors, tiles and wall and floor finishes, among other things. This makes each owner-occupied apartment a piece of customization. To facilitate the choice for residents, not only have specific showrooms been set up, but a resident supervisor has also been appointed."

In the spring of 2021, BESIX Nederland will deliver all work.