Load-bearing concrete floor elements that are a mere two centimeters thick offer great stability without needing the reinforcements typically used in concrete construction. The floor design harks back to historical construction methods, including some used in Gothic cathedrals.

Philippe Block stands on a floor prototype printed using sand. Image credit: ETH Zürich/Peter RüeggThe impetus for reducing the thickness of concrete floor slabs comes from multiple directions. Thinner floors would allow a builder to add more floors in the same amount of space or to reduce the necessary space to accommodate the same number of floors. Using less concrete—which is not an environmentally-friendly building material—saves construction costs and reduces the amount of CO₂ released during concrete production.

Researchers at ETH Zurich’s Institute of Technology in Architecture studied several construction methods, including the Catalan vault. This vault construction, which features narrow vertical reinforcing ribs, inspired the team’s design for concrete floor slabs.

Using computer software, the team calculated how to arrange the rib reinforcements for optimum distribution of compression forces during loading. The ribs converge at the slab’s four corners. The supports are connected by a set of steel ties that absorb the horizontal forces. The slab can absorb an asymmetric load of 4.2 tons, which is two and a half times what Swiss building codes require.

The research team also used 3-D printing to produce the first slabs, eliminating the need for expensive double-sided molds.

The research team’s next step is to test the new floor at the NEST research building in Dübendorf. A two-story penthouse to be built on NEST’s roof will be constructed from the concrete floor slabs.