Platform on new construction, renovation, restoration and transformation
Schöck is the leading specialist in high-quality connection components for structural, static, and construction applications—ranging from thermal and sound insulation to anchoring and reinforcement technology. Popular items in the product line include the Isokorf® structural anchoring solutions, which ensure reliable balcony anchoring, reduce heat transfer, and thus prevent energy loss. The Isokorf® anchors were first introduced in 1979 and revolutionized the construction industry. And even in 2025, these products continue to make a big impression. For example, at Hotel De President in Hoofddorp.
Hotel De President is an impressive project that combines sustainability and modern design. The hotel covers an area of 13,000 m² and has 249 rooms of various sizes. In addition, the complex features modern facilities such as a reception area with a lobby, a breakfast room, a restaurant, a bar, kitchens, meeting rooms, a fitness center, and a recreation area. The building’s design follows the bends and curves of the street, creating an exciting facade. This effect is enhanced by the stepped, staggered facades, facade bands in white architectural concrete, and over 300 prefabricated balconies.
In the summer of 2023, Schöck was approached by De Jong’s Betonbedrijf BV from Maarssen to prepare a quote for the balcony anchors. The contract was awarded immediately after the summer, after which Schöck engineer Remco Bolhuis began working on the technical design. “Our assignment involves anchoring more than 308 precast balcony slabs,” he explains. “In addition to roof slabs, these were mostly concrete canopy slabs, which are mounted above the windows and are not accessible to pedestrians. 291 slabs were anchored directly using our Isokorf® elements, while 17 bridge slabs were indirectly supported on the adjacent slabs using a toothed connection. Two to three Isokorf® elements are used per balcony slab, which means we supplied a total of over 700 anchors.”
What sets Schöck apart is that its anchoring solutions always come with engineering and calculations included, Bolhuis emphasizes. “As a supplier, we’re able to perform highly targeted and specialized calculations. This allows us to apply our products very efficiently. For every component in the cage, every rebar, and every compression stud, we can precisely calculate how much force passes through it and how much of that force is utilized. Moreover, we know exactly which cages are available and what they can be used for. This ensures that clients receive an efficient design with minimal thermal bridges, the highest possible insulation values, and minimal material usage.”
During the engineering phase for Hotel De President, Bolhuis first assessed the number of balcony slabs and their variants. “The same applies to the loads acting on these balcony slabs,” he explains. “What wind loads need to be taken into account? And what will be placed on the slabs? Will people be walking on the balcony slabs or not? And what does this mean for the forces acting on the suspension system? Based on this information, the correct types, sizes, and capacities of Isokorf® anchors were selected. In addition, I calculated the correct positions for these anchors. All of this information was then compiled into a technical report for the municipality and the balcony slab supplier—as well as for the contractor on site, who now knows exactly how the anchors should be installed.”
One unique aspect of Hotel De President was the early strength calculation, Bolhuis explains. “The contractor wanted to know whether the Isokorf® anchors could already support the balconies before the concrete had fully cured. In this project, they wanted to subject the balcony floors to a stress cycle. By briefly loosening the support props, the concrete would be briefly placed under stress to promote better curing. This is an approach we’re seeing more and more often in projects, and it means we have to perform calculations not only for the final phase but also for the construction phase.”
“The majority of the connections at Hotel De President were concrete-to-concrete connections,” Bolhuis summarizes. “A few canopies were suspended in areas where there was no floor behind them—for example, because these areas were designed to be open spaces or voids. In these areas, a steel girder was installed, which required a concrete-to-steel connection. Here, too, we were able to provide an excellent solution by incorporating a concrete-to-steel Isokorf® in the opposite direction. In this project, steel balcony slabs are not suspended from concrete floors; rather, concrete balcony slabs are supported by steel beams. By installing the Isokorf® anchors in the reverse direction, they can still absorb the forces in the correct direction.”
