Intensive collaboration leads to ingenious solution for residential tower block on Piekstraat

Balanced mix of tunnel formwork, structural scaffolding, facade scaffolding and structural end wall

The island of Feijenoord, an area in Rotterdam South, is currently the scene of a feat of concrete construction. At the head of the island, surrounded by water and industry, the Piekstraat project is being realised. A residential tower is rising up on a postage stamp-sized site, appearing to be constructed from four stacked blocks. The four stacked volumes protrude on all sides of the building. This poses enormous architectural, structural and logistical challenges. Heijmans Utilitaire Woningbouw and Hendriks worked closely together to develop ingenious solutions.

Postage stamp-sized construction site

Piekstraat is the name of the new 73-metre-high residential tower, which will comprise a total of 142 loft apartments. There is a wide variety of homes on offer: no fewer than six different types, ranging from Water, Drive-in and Panorama lofts to Sky, Maas and Atelier lofts. The arrival of the residential tower heralds the development of the Feijenoord island. The location is fantastic in many ways: views over the water, views of the skyline and the city centre within easy reach. Less fantastic, but therefore more challenging from an architectural point of view, is the size of the construction site, which is almost as large as the floor area of the residential tower itself. This poses a considerable challenge in terms of the supply, removal and storage of materials; a nearby pontoon even has to be used for the storage of materials. Building on a postage stamp in its best form!

Tunnel casting as a construction method

You only really realise how challenging Piekstraat is when you stand on the construction site. The various structural solutions that have been devised to enable practical construction despite all the cantilevers are impressive. At the construction site, we meet Werner Bruijns and Marco van den Burg from Heijmans Utilitaire Woningbouw. The construction method chosen is tunnel casting with a concrete core that is poured on site. Because these walls are constructed after the tunnel process, lightweight aluminium formwork has been chosen here. "Tunnelling offers flexibility for the different shapes of the homes," says Werner Bruijns. "The big challenge lies in the cantilevers. They cause structural headaches. Hendriks dared to take on that challenge. Hendriks not only had complete confidence in the solution we developed together, but also showed the courage to get started with it."

Unity in diversity

The development process clearly demonstrated the scale of the challenge. Marco van den Burg: “Despite the wide variety in construction volumes and between the homes, we wanted to try to incorporate everything into a single system. Unity in diversity, you might say. In the end, we succeeded, but it took a period of collaboration and engineering work by the specialists at Heijmans and Hendriks. Thanks to their joint engineering efforts, the ideal mix was achieved between tunnel formwork, structural scaffolding, façade scaffolding and structural end walls. The result is a residential tower whose shell is being built without scaffolding, as it were.”

Colossal superstructure

The structural basis for the construction of the residential tower is formed by a superstructure that hangs like a table from the façade of the building. Werner Bruijns:
“The combination of structural scaffolding and structural headboards is necessary to realise the cantilevers. The colossal scaffolding and headboard construction is supported by yokes that transfer the load to the lower part. The giant superstructure will be converted twice during construction to realise the higher cantilevers. Hendriks has a team of specialists on standby to convert the structure.”

Safe relocation of façade scaffolding

From the structural scaffold, work is carried out using façade scaffolds that are raised as the building grows. "The construction crane and Hendriks' double-acting hydraulic compensation cylinder are used to move the scaffolds," says Marco van den Burg. "At the bottom, the façade scaffolds rest on a support angle. The compensation cylinder ensures that the scaffolding can be hydraulically detached from the building. The scaffolding can then be raised as a whole to a safe distance from the façade."

Directly felledt

Heijmans is using four tunnels to construct the floors, two of which are used for pouring and two for building. The cantilevers are being constructed using a half tunnel placed on the structural scaffold. For maximum safety, the tunnels are extended on the water side. "Once the tunnel is out, we immediately install the timber frame façade with aluminium window frames and glazing. This will be finished with metal façade sections at a later stage."

Excellent cooperation

When we ask Marco and Werner about working with Hendriks, they say, “This is a project whose success depends on cooperation between the parties involved and optimal use of each other's expertise. We have been working with Hendriks from the very beginning to solve the challenges of this project. We have been largely successful, and the entire construction team deserves credit for that.”