Klaasje, Amstelveen: Roof park forms fine residence and walking route for future residents and passers-by

Construction combination De Nijs - Huybregts Relou started construction of the residential towers designed by LEVS architects from Amsterdam in late 2018. The architecture has a chic appearance with various architectural features of the surrounding 1960s buildings reflected in the design. The buildings are characterized by plinths that are staggered in height and variation in façade material on the third, fourth and sixth floors. On the top layer, facades with bronze-colored aluminum panels give the whole a warm appearance. All buildings stand on an underground parking garage that runs under the entire site. A roof garden is currently being realized on this underground parking garage that blends seamlessly with the surroundings. idverde Realisatie was responsible for the technical design of the roof garden, including the adjoining outdoor garden section, and is currently carrying out the construction.

The design of the roof garden and outdoor garden section was created by BuroScope and consists of approximately 50% of greenery and approximately 50% of various types of paving. The design is characterized by playful walkway structures with angular "points. It has the same design as the adjacent site of Klaasje phase 1 and thus (soon) forms an attractive whole. The design connects to the large number of senior residents. The design also includes space for hedges separating the private terraces from the first floor dwellings and several triangular raised planters with multi-stemmed large shrubs and benches. Various light poles and bollard lights atmospherically accentuate the walkways and give it a park-like appearance at night. 

Artificial groundwater table

Since the roof garden will be installed on a parking basement, a two-layer fully adhered root-resistant roof covering was applied to the concrete structure. To test the waterproofing, a water test was performed prior to the realization of the roof garden. After this test, installation of the Optigrün roof park roof garden system began. This roof garden system consists of a felt-like 5 mm thick protective cloth placed directly on the roofing. A 100 mm thick layer of coarse lava granulate is then applied to this cloth. In this layer, during the growing season, there is a 70 mm layer of water, or artificial water table. This layer of water is created because all the rainwater drains in the deck are fitted with 70 mm high standpipes and a curb is placed on the edges of the basement deck. This creates, as it were, a bathtub that is normally filled by rainwater and can be replenished by tap water during prolonged drought. The vegetation then always has water available from below. A filter fleece is placed on top of the lava granulate layer on which a layer of intensive roof garden substrate is applied in the area of the vegetation as a nutrient medium. At the level of the paving, layers of rubble and road sand are applied to provide a stable foundation for the paving. At the level of the rainwater drains, recesses in the growth and paving layer are provided with inspection chutes.

The walkways are provided with concrete clinkers with a natural stone granulated top layer of the Breccia type by the Struyk Verwo company. These bricks consist of three different shades of gray that are mixed and applied in herringbone bond. The private terraces have sand-colored concrete tiles in block bond. In terms of landscaping, several lawns (partially rideable) are present. The hedges consist of native field maple that grow fairly quickly and eventually form dense hedges. There are also several perennial planting areas with about 20 species of herbaceous and ornamental grasses. These plant species are characterized by flowering from March to late November, varying in heights from 30 to 80 cm and being attractive to insects. Finally, substantial multi-stemmed currant trees will be planted in the raised planting beds. These spring-flowering deciduous plants have whitish flowers, edible berries and beautiful fall colors.

Nice solution

The roof park will become a nice place to stay and walk for future residents and other passers-by. It adds greenery to a rather densely built-up area, can buffer a lot of rainwater and also removes countless parked cars from view. All in all, a beautiful solution to combine various functions in an inner city environment and to make the public space more climate proof.