Recypark in Anderlecht, Belgium, makes circular economy a pleasure

Recyparks are an increasingly popular resource in Brussels, enabling residents to offload their waste and unwanted bulk items in locally-situated shipping containers ready to be taken away for reuse or recycling.

A 2016 architectural competition launched by regional waste management organisation Bruxelles-Propreté called for the design of a new Recypark on a 5,000m² plot running alongside the main canal in the centre of Anderlecht, a major municipality in the region. 

The concept of reuse was at the heart of the brief. The competition-winning design, by architects 51N4E and Witteveen & Bos with materials salvage company Rotor, proposed a combined Recypark and public skatepark/green space, housed in a large open-sided hall supported on a repurposed structural frame.

Doing it differently

A pioneering approach, involving the disassembly, transportation and storage of an existing structure, followed by its reassembly on site, was a first for Belgium, challenging conventional approaches to design and public tendering.

An initial research phase in preparation for the competition saw Rotor identify four existing buildings with appropriate structures for the hall and 51N4E develop a ‘loose-fit’ design that could be adapted to accommodate each of them. The skatepark aspect of the scheme was designed by Witteveen & Bos for under the east side of the hall, helping to encourage the scheme’s acceptance in the neighbourhood.

Bruxelles-Propreté eventually settled on a former equestrian centre slated for demolition in the city of Liège, around 100km from Brussels. Its 26m-wide boomerang-shaped glulam timber arches were in a decent state of repair and would give the project a strong identity.

In an unconventional move for a publicly-funded project, the client bought the hall from the owner before detailed design and had the frame carefully dismantled during demolition and stored in a warehouse in Nivelles, south of Brussels.

Alternative opportunities

Yann Gueguen, architect at 51N4E says: ‘It was nice to be able to work with timber as we would never have chosen it if we were starting this project from scratch. Steel is generally much cheaper than new timber, faster to erect, and avoids fire protection issues.’

There were many complexities attached to reusing historic timbers, but the architect implemented design strategies to help mitigate the risk, notably reserving salvaged elements for less demanding parts of the structure (around half the arches are new), over-dimensioning them and designing specific reinforcements.
There was a lack of documentation on the existing building, including its age – it is thought to have been built between 1970 and 1980 – dimensions of the timber beams and method of fabrication.

Visual investigations revealed that several arches were too badly damaged to reuse and the bases of the others were rotten or had been chewed by horses. It was decided to cut them 1m from the bottom and mount them on concrete bases. Similarly, the tapered ends of the beams, at the top of the roof pitch, were cut and replaced with steel connections.

Project requirements changed as the design evolved, affecting the approach to reuse. For example, a decision to reorient the angle of container loading decks, accessed via gaps between adjacent arches, effectively widened the gaps, lengthening the required beam spans and ruling out the use of existing arches over that section of the hall. 

Reused beams are instead grouped together in a tighter arrangement at the north end of the hall covering a ‘small fractions area’ including a ‘recyclerie’ where objects in good shape can be picked up by other residents. 

These beams were installed in pairs – two half arches bolted together – to increase the load bearing capacity. In all, 20 arches taken from the riding centre were installed, with the remaining 17 beams newly-manufactured versions.

Improvised solutions

With no recognised working methodology for this form of reuse, the project team was forced to improvise solutions when it hit obstacles.

Gueguen says initial destructive testing to verify the structural performance of each glulam proved an inaccurate and arduous process that started to delay the construction programme. As a result, Belgium-based engineer Greisch was appointed at a late stage to take responsibility for the structural design of the reused glulam and to verify its structural performance.

A chain of custody document was also produced, on the advice of Rotor, containing all information on the timbers gathered during the competition phase and setting out precise responsibilities of every stakeholder involved in reuse, including the design team and contractors. The document was a form of contract signed up to by everyone involved.

‘The goal was to set responsibilities for each actor so that if something went wrong we didn’t start to point fingers. There was now a clear mission from the start to the finish line,’ says Gueguen.

Independent checks

In another step away from the construction norm, engineering partner Seco Belgium was brought onboard as an independent external supervisor to double-check all the calculations and verify quality throughout design and execution, including delivery on site. This proved vital in convincing insurers to underwrite the project.

Although Greisch had extensive experience of building renovations and upgrading existing structures, Recypark was its first job testing and designing for reused components.

Undamaged samples of beams not being used in the building were subjected to multiple tests, including for timber type and density, bending resistance, and the impact of ageing. A spectrograph test identified the type of glue used for lamination. In assessing the architect’s structural design, Greisch found that all bending and shear forces decreased, and stresses were relatively small compared to the original building. 

Arnaud Pineur, timber expert and project director at Greisch, says: ‘We concluded that the architect’s design, which is based on conservative assumptions and almost no information about the structures, could have been significantly scaled up to support larger loads, if necessary.’

The engineer was also required to verify the stability of the structure based on Eurocodes, which do not yet take into account reused components, so performance had to match that of a structure made from newly manufactured components. 

‘Design codes are based on a typical structural lifespan of about 50 years and we were reusing a structure that was already 40 to 50 years old, so we had to make sure reusing it was not going to be a problem,’ says Pineur, adding that this was the trickiest part of the job.

Finding a solution meant revisiting the original scientific article used as the basis to develop the Eurocode in order to recalculate a safety coefficient value for the structure’s extended lifespan.

‘We concluded that the impact of the reused structure, and its ageing, on the safety coefficient is pretty limited, and the Recypark structure should last for another 50 years,’ says Pineur. 

Much like a skatepark, the project had its ups and downs, as reflected in the eight year timeframe between concept and handover this September. Clearly the industry has a way to go before a fully developed reuse circuit for this kind of structural component is in place.

Materials salvage companies like Rotor operate in Belgium, and are building business models based on the collection, qualification and selling of reused items in large enough quantities to service markets like construction.

What next?

The main goal for the future, says Pineur, is to ensure that these individual initiatives work together to create a system, ‘perhaps at the scale of a country’, to deliver in sufficient volumes to support the design and delivery of buildings. Timing and storage issues must also be addressed, he adds, to ensure that a resource that is available today can be bought and made available to build when a project gets to site. 

On a positive note, Gueguen says the overall cost of choosing reused glulam on Recypark was equivalent or slightly cheaper than building the arches new, despite the additional overheads related to transport logistics, renting a storage facility, materials studies and testing etc.

Recypark’s approach has also changed the attitude of main contractor Eiffage, which now plans to incorporate multiple reused elements in the conversion of a historic synagogue into a dance school in Belgium. 

‘The most important thing we learned is that we can build with materials from existing buildings, removing the need to fabricate new products,’ says José Rangel, project manager  at Eiffage. ‘It’s important to look for products set for demolition and give them a second life … you have to change your mindset and be convinced you will find what you need,’ he concludes.