31,000 m2 of wide slab floors for Merwede Cix City

A vibrant inner city district, with ample attention to greenery and a broad mix of housing and facilities. That is the Merwede project in Utrecht, which should provide space for some 6,000 new homes for 12,000 residents. At the end of 2025, Bouwcombinatie Merwede (Bouwonderneming Stout and Trebbe) started the realization of Merwede Cix City (formerly Merwede Blok 13), which with more than 40,000 m2 will be a small city in itself. At the base of the block are a semi-underground parking basement and a two-story commercial plinth with an activity center, retail spaces and a supermarket. On top of this will be ten apartment buildings with a total of 306 apartments, in a square shape around a collective courtyard. Especially for Cix City, De Hoop Pekso will draw, calculate and deliver 31,000 m2 of wide slab floors, which will provide a stable and even floor construction from the ground floor of the residential buildings.

“In early 2024, we were approached by Merwede Five (a development combination of Lingotto, Blink and Nuvia Real Estate), to come up with a technical design and budget for Cix City in a construction team structure,” says Michel Renzenbrink, project manager at Stout Construction Company. “Because of the scope of the work, we sought collaboration with Trebbe. We then jointly arrived at a technically ready design and contract price and, in collaboration with the architect and structural engineer, we further developed the execution design and detailed planning.” Drilling of the foundation piles began in early December 2025, he says. “The realization of Cix City will then take about three years.”

Concrete construction with wide slab floors

“At the base of Cix City will soon be a cast-in-place concrete structure with concrete walls and wide slab floors, combined with steel and hollow-core slabs,” Renzenbrink says. “The buildings will be finished with facade-filling wood frame elements with various finishes. Think of different colors of brickwork, aluminum cladding, balconies and fencing, giving each building its own identity.” He says the choice of wide slab floors is a logical one because they are the most common floor floors for residential construction. “In the compression layer of the floors, the pipes for the WTW system, water and sewage are included, among other things. In addition, Isokorf balconies are anchored to the wide slab floors. The construction of the floors naturally takes this into account.”

Good and long-term cooperation

For the wide slab floors, Bouwcombinatie Merwede works together with De Hoop Pekso, because of the good price-quality ratio, excellent engineering, fine communication and delivery reliability, says Renzenbrink. “Moreover, both Trebbe and we can fall back on a good and long-term cooperation.” Normally, Iposim, the construction agency of De Hoop Pekso, calculates and draws the floors, explains Rayon Manager Ron van Beusekom of De Hoop Pekso. “Mustafa Sert and Ronald Buitenhuis of Iposim are the structural engineers and permanent points of contact for Bouwondernemng Stout and Trebbe, respectively, but because of the complexity of this work, we decided to place it with our partner SKS Engineering. SKS works out all plates and plate layouts in BIM, so that Bouwcombinatie Merwede can draw in its recesses. Then we can also make the 2D reinforcement drawings, so that the braider can soon be well prepared for construction.” The floors have already been structurally calculated, he says. “In June 2026, the first wide slab floors should be delivered. For this, we are working with a secure link, which allows the contractor combination to call all freights with wide slab floors just-in-time.”

31,000 m2 of wide slab floors

In total, De Hoop Pekso draws, calculates and delivers 31,000 m2 of wide slab floors for this project. “Our wide slab floors are reinforced system floors poured with traditional gravel concrete,” Van Beusekom explains. “The floors are constructed from a concrete shell of 50, 60 or 70 mm, which is provided with constructively required plate reinforcement and continuous lattice girders. In addition to their constructive task, these lattice girders also act directly as lifting points.” The floors are prefabricated in De Hoop Pekso's own factory in Oosterhout and under the best climatic and working conditions, he says. “This cleverly eliminates clashes and failure costs during execution.”

Great freedom of form, neat connection

Major advantage of the wide slab floors of De Hoop Pekso is the great flexibility and freedom of form, says Van Beusekom. “The piping is easy to incorporate into the compression layer, while auction edges guarantee a good mutual connection. Our wide slab floors have very good soundproofing properties. In addition, they are excellent at meeting fire resistance requirements of 30, 60, 90 or 120 minutes. Thanks to the smooth underside, the floors are immediately ready for spraying.”

Four-sided calculated

To meet Cix City's fire resistance requirements, these wide slab floors will have a 60 mm concrete shell, Van Beusekom said. “In one of the buildings, even a 70 mm thick shell is used. The floors here are calculated four-sided, so they can transfer their forces on four sides to the columns.”