Heart of the Waalsprong, Nijmegen: Project of large numbers

In Nijmegen-North, the contours of Hart van de Waalsprong are already clearly visible. The impressive and sustainable planning area of more than 6 hectares will offer space for 500 houses and apartments, approximately 11,900 m² of center functions and smart parking and mobility solutions from the end of 2024. As a first project phase, the Donk and Elft buildings were realized, with 81 owner-occupied apartments, 140 (social) rental apartments and stores. Winans Dakwerken realized approx. 7,000 m² retention/buffer roofs and terrace roofs for both buildings. In addition, the Blokzijl-based roofing specialist was responsible for the realization of approximately 8,000 m² parking roof, between the two buildings and at 5 meters above ground level.

"The upper roofs of Donk and Elft will be constructed as retention/buffer roofs, buffering water 24/7," says Peter Dibbets, Operations Manager at Winans Roofworks. "Because rainwater has a cooling effect, the temperature of the floors below will stay lower." The so-called blue roofs are designed as compact roofs. "We first poured the roofing, after which a cementitious EPS mortar was applied," Dibbets said. "Then we applied a special two-layer roofing material that is suitable for permanent (water) loads. When heavy rainfall is predicted, the water on the roof is already drained to various wadis in the area, so that sufficient capacity is available to collect 'new' rainwater. This relieves the municipal sewer system."

Several building roofs are designed as terrace roofs. "These roofs feature PIR insulation and bituminous roofing, which is suitable for the installation of terrace tiles," Dibbets said. "In addition, we have performed several roofs with regular roofing, slope insulation and a raised drain to retain rainwater for <24 hours. Most special, however, is the parking roof with 224 parking spaces. Here we provided a poured roofing system with a poured layer, root-resistant roofing and XPS insulation, on which a parking roof system with tiles was then installed. The final work was completed at the end of October."

Winans Dakwerken was acquired in early 2023 by Wessels Bouwgroep, which also includes Wessels Vakbouwers. For the Donk and Elft buildings, Wessels Vakbouwers provided the setting work for the masonry profiles and the complete facade insulation, says foreman Tom te Molder. "In addition, we were responsible for the masonry work, some of which was carried out from our own lifting scaffolds. A total of 25 masons processed 835,000 facade bricks, at a peak rate of over 50,000 bricks per week. Quite a feat, because the many masonry connections and facade detailing made the work complex. As soon as a facade was completed, Winans Dakwerken immediately started assembling the roofing. To guarantee the watertight connection of facades and roofs, the correct detailing was already determined in the engineering phase."