Elementa, Basel

In pursuit of a circular economy, designers are increasingly looking for ways to reuse the structural elements of a building. But how do you design something when its constituent parts are still part of another building on a different site? It starts with a catalogue. At least, this was the experience of Swiss architect Parabase when it entered the international open competition run by the city of Basel for 120 affordable homes and an integration centre for migrants. “With the brief, the city provided a catalogue of demolition components that we could reuse,” says Pablo Garrido Arnaiz, partner at Parabase, which is now preparing to build its winning entry. “Everyone had the same information, but I think we were somehow the ones who made most use of the different pieces.”

Most of the elements will be taken from the nearby Lysbüchel car park, earmarked for demolition in 2024. Circular planning consultant and “component hunter” Zirkular made an inventory of more than 60 building parts, categorized into structure, surfaces and fixtures, and covering everything from ribbed slabs to urinals. Each entry included an extensive factsheet, showing dimensions, weight, number of available pieces, and links to plans, sections, photographs, original reinforcement drawings and any other data. For structural elements, test sections were removed for analysis and testing at the EPFL technical university in Lausanne, enabling strength characteristics to be included in the catalogue.

Zirkular also calculated an embodied carbon saving for each component, which allowed the designers to quickly assess the reduced footprint of their proposals. Parabase’s scheme, known as Elementa, will reuse 2,680 components from the car park and other catalogued sites, saving the equivalent of 1,088,082kg/CO2. Parabase came up with two housing types, using different catalogued items from the car park as loadbearing structure.

A four- storey block repurposes columns and beams as an external frame, integrated with new concrete elements to make a grid and floor height suitable for housing. Recycled corrugated metal becomes the outer layer of the facade. The other three- storey housing type uses ribbed floor slabs as a loadbearing external wall, stacked vertically then horizontally like a brutalist Stonehenge.

As architecture, it’s about establishing a set of constraints and prioritising these above aesthetics, says Arnaiz, citing Jean Nouvel’s Nemausus social housing in Nimes (1987) as a precdent. There, fixtures such as metal stairs and outsized garage doors were specified from industrial catalogues to minimise costs, while greater attention was paid to space and layout.

At Elementa, an important element of the architectural design will be the connection between old and new – details such as brackets and beam edges. “It’s not like a unified system where everything fits perfectly together. These elements have different dimensions, use different materials, behave differently.”

 Internally, the homes will have to adhere to strict design codes, but he expects them to bear traces of their unconventional heritage. There is a lot of work to do before the project reaches that stage, and Parabase’s role extends far beyond a traditional architectural brief. “We also have to coordinate how the car park is going to be dismantled,” Arnaiz says. “We have to store the pieces on our plot, which is a huge logistical challenge. Already, at the start of the process, you have to know how you are going to build your building.”

Each element has been given a QR code to help with tracking, but the journey to their final destination in the new building has to be plotted with precision. “Some of these pieces are five or six tonnes, so if you need one that you’ve stored at the bottom of a pile, that’s not going to work. We already know the position where they’ll be stored, and even where the cranes are going to be located.”

The architects are also working closely with other consultants on a legal framework to ensure a 40-year design life for the buildings. “There is no template or established way of proceeding. Everything is new.” Arnaiz points out that, even armed with Zirkular’s factsheets, they are introducing unknowns by changing the use of precast elements – from slab to wall, for example. “For some of the concrete, the reinforcement bars were allowed to be close to the surface. So that is then an issue that we need to solve.”

Disassembly of the car park will begin in April and the development is slated for completion in 2028.

Photo and CGIs Parabase