A comparison of recent competitions for cantonal schools in Zurich from 2022 – 2024 shows that, on average, a ratio of approximately 1:5 between sealed area and floor area is achieved. Our project proposes to achieve cost, construction time and CO2 savings of 10% by achieving a maximum ratio of sealed area to floor area of 1:10 and thus minimising the underground volume. This reduces solid construction – usually reinforced concrete – to an absolute minimum within the plot and the necessary program. A large part of the costly sealing, excavation and shoring structures is also eliminated. These economies allow an optimised construction time, as the comparatively small underground area plus the column foundations can be erected quickly and all upper floors can be highly prefabricated as fully demountable timber-steel hybrid constructions. In this case, the economic advantages go hand in hand with the ecological benefits. The ambitious target of a maximum of 1:10 sealed area to floor area can become a model for cost-effective and CO2-optimised school buildings and represents the core statement of the required ‘pilot project’. But what does the maximum reduction of underground areas mean for urban planning, landscape and architecture?
Soil and water are fundamental resources of the city that need to be protected. Both are present on the site, but are sometimes hidden under asphalt. Based on this assumption, the project proposes to unseal the site over a large area and to seal less area than before with the new building. The result is a timber construction that is almost completely elevated above the ground, rising from the terrain, with only the shelters required by building regulations in the ground. The small, naturally formed body of water is preserved and maintained as a retention and climatic area. It may not always be obvious, but even in the unused and unmanaged spaces of cities, there are complex relationships that are worth protecting.