Glass greenhouse with walkway above the treetops.

The Hortus Botanicus of the University of Amsterdam (UvA) has been situated on the Nieuwe Herengracht since 1692, and for many years it enjoyed a high international regard. However, in 1986 the UvA decided to close the Hortus because of cost-cutting measures and the fact that changes in the study of biology meant that a plant garden was not such a necessity. Because of the dilapidated state of the complex, most of the greenhouses were demolished. Much of the plant collection was moved elsewhere.

On the initiative of the Vereniging Vrienden van de Hortus (Friends of the Hortus Association) a campaign was launched in order to save the Hortus and open it to the public. Refreshment facilities were added. The main priority in this initiative was the construction of a new greenhouse to reconsolidate and house the dispersed plant collection.

The Hortus greenhouse has a surface area of about 1,500 square metres and a height that varies from 4 to 11 metres. The greenhouse is subdivided into three zones for different types of climates: a tropical, a subtropical and a desert climate, separated by glass walls.

In view of the location in the midst of the grachtengordel (Amsterdam’s historic ring of canals) it was important that the greenhouse was sensitive to the existing urban structure. In their scale, rhythm and orientation, the glass walls and roof alongside the Nieuwe Herengracht are responsive to the canalside houses opposite. The arched roof slopes down towards the garden, which is therefore shade-free and has an intimate character.

In order to reduce costs, the design makes as much use as possible of mass-production greenhouse components as a membrane over the load-bearing structure. The main load-bearing structure was designed as slenderly as possible for optimum daylight in the greenhouse. The structure is based on the ‘tensegrity’ principle. The stability is ensured by a system of columns that function as compression members and thin tension members that keep the construction rigid.

High up in the glasshouse there is a steel walkway with a glazed floor, offering a view of the treetops. The bridge’s structure consists of a round tube, which also supports the handrails and the supports for the glass floor.

Architect: ZJA
Client: Stichting interimbeheer Hortus Botanicus Amsterdam
Engineering: ABT Velp
Design: 1990-1992
Inauguration: 1993

Project: 0025