Rotterdam Netherlands

The spring of 2023 saw the completion of the Salix project in the Hillegersberg-Schiebroek district of Rotterdam. In total, the project comprises 74 new rental houses and apartments for families, first-time buyers and senior citizens. Salix consists of 4 residential blocks, a multistorey carpark and a variety of public access outdoor spaces.

Outdoor space for everyone

The Salix project was undertaken by Accresco and Van Wijnen Dordrecht. Green was a central element of the design. Everyone needs access to green space, and that goal has been achieved, with balconies, rooftop terraces and a communal rooftop garden, for everyone! Every Salix apartment or home has its own terrace or balcony. In addition, a communal rooftop garden has been created on top of the multistorey carpark. Thanks to its central location, this communal garden is the perfect meeting place for residents.

Rooftop garden layout

The rooftop garden, laid out by idverde, is a green oasis in the city. Roeland Pullen, rooftop and facade greening consultant at idverde talked about the process. “Everything was laid out within just one month; 5 weeks if you include the planting. The entire rooftop garden was first entirely submerged by us, for a waterproofness test. This stage was followed by the laying out of the rooftop terraces, the substrate and the planting. The new rooftop garden features 45 different varieties of plants, including geraniums, asters, lavender, irises, yarrow and fountain grass. In other words, a wide variety of plants that thrive in dry conditions.”

Stability and weight

For the paving of the rooftop terraces and the communal rooftop garden, idverde selected the rooftop slab system from Zoontjens. Roeland Pullen explained his decision to choose Dreen®Nxt. “We identified the system as an excellent solution in this situation, in connection with both its stability and weight. Except for the strips where the plant trays have been placed, a weight limit of 200kg/m2 was imposed on the rooftop terraces. There is also a wooden pergola, which is partly anchored to the plant trays. As a consequence, the load distribution differs slightly, across the site. Dreen®Nxt is a rooftop slab system that fits perfectly within the limit.

Levelling the height difference

For the Salix project, the Dreen®Nxt system offered yet another advantage. A considerable height difference needed to be bridged. Roeland Pullen explained, “At some points, a height difference of up to 30 cm had to be bridged, for example between the sections along the facades and the centre of the rooftop garden. With this system, even those height differences could be perfectly straight. At the end of the day, the entire walking area was installed perfectly tight and level. And it provides additional support for the heavy plant trays.

With regard to stability and weight, we found the Dreen®Nxt system to be a great solution here. You can also level slopes beautifully with this system

Roeland Pullen