Platform on concrete and steel in construction
One hotel, 308 balcony slabs, over 700 anchors
Schöck is the specialist in high-quality connection components for structural, static and constructional applications. From thermal and sound insulation to anchoring and reinforcement technology. Popular in the range are the Isokorf® structural anchoring solutions, which provide reliable balcony anchoring, reduce heat conduction and thus prevent energy loss. Isokorf® anchors originated in 1979 and revolutionized the construction industry. And even in the year 2025, the products are still making waves. For example in 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 square meters and has 249 rooms of various sizes. In addition, the complex features modern facilities such as a reception area with lobby, breakfast room, restaurant, bar, kitchens, meeting rooms, fitness room and entertainment area. The design of the building follows the curves and curves of the street, creating an exciting façade image. This effect is enhanced by stepped staggered facades, gable bands in white architectural concrete and over 300 prefabricated balconies.
Schöck was approached in the summer of 2023 by De Jong's Betonbedrijf BV of Maarssen, to provide a quotation for the balcony anchors. The order followed immediately after the summer, after which engineer Remco Bolhuis of Schöck started the technical development. “Our order includes the anchoring of over 308 precast balcony slabs,” he says. “In addition to roof slabs, this mostly involved concrete canopy slabs, which are mounted above the windows and are not walked on. 291 slabs were anchored directly with our Isokorf® elements, while 17 bridge slabs were laid indirectly to the adjacent slabs with a tooth bearing. Two to three Isokorf® elements were provided per balcony slab, meaning that we supplied a total of over 700 anchors.”
Unique to Schöck is that the anchoring solutions are always delivered including engineering and calculations, Bolhuis emphasizes. “As a supplier, we are able to make very specific and specialized calculations. This also allows us to apply our products very efficiently. For every part in the basket, every reinforcement bar and every compression cam, we can calculate exactly how much force passes through it and how much is exploited. We also know exactly which baskets are available and what is possible with them. As a result, clients are assured of an efficient design with minimal thermal bridges, the highest possible insulation values and minimal use of materials.”
In the engineering phase for Hotel De President, Bolhuis first inventoried the number of balcony slabs and variants. “The same applies to the loads acting on these balcony slabs,” he says. “What wind loads need to be calculated with? And what will be placed on the slabs? Will the balcony slabs be walked on or not? And what does this mean for the forces that occur in the suspension? Based on this information, the correct types, sizes and capacities of Isokorf® anchors were selected. Furthermore, I calculated the correct positions of these anchors. Then all the information was converted into a technical report for the municipality and broad plate supplier. But also for the contractor on the construction site, who thus knows exactly how the anchors should be applied.”
A special feature at Hotel De President was the early strength calculation, says Bolhuis. “The contractor wanted to know whether the Isokorf® anchors could support the balconies even before the concrete was fully cured. In fact, in this project they wanted to shock the floors of the balconies. By loosening the support struts for a moment, the concrete would briefly come under tension to promote better curing. An approach that we see more and more often in projects and that means we had to make a calculation not only for the final phase, but also for the construction phase.”
Most of the connections at Hotel De President involved concrete/concrete connections, Bolhuis summarizes. “A few canopies were suspended where there was no floor behind them. For example, because an open space or void was provided in these places. At these places a steel beam was made, which required a concrete/steel connection. We were also able to provide this excellently, by including a concrete/steel Isokorf® in the opposite direction. In this project, in fact, steel balcony slabs are not suspended from concrete floors, but concrete balcony slabs from steel beams. By applying the Isokorf® anchors in reverse, they can still absorb the forces in the correct direction.”
