Material reuse towards circular architecture

Demolishing a building and sending everything to the skip is no longer a given. Across Wallonia and Brussels, public authorities, clients and designers are learning to see an existing building as a stock of materials. Here is how we approach reuse at STARC and Optibim, with project examples and useful regional pointers.

Why reuse is becoming essential today

The construction sector consumes vast amounts of materials and generates a large share of all waste. Bruxelles Environnement (Leefmilieu Brussel) points this out in its training materials: Brussels buildings account for 50% of raw materials use, 35% of total waste production and 91% of waste sent for recycling, mostly in the form of "downcycling". In other words, even when recycled, most materials lose value.

Reuse goes further still. According to the Guide Bâtiment Durable (Sustainable Building Guide), reused materials are materials that have been dismantled during deconstruction work and are put back, or intended to be put back, into use in a new project. A door remains a door, a brick remains a brick. No shredding, no remelting.

This is not, in fact, a new idea. As Rotor points out, reusing materials was historically the norm in the construction sector. In our quadrangular farmhouses and village houses, lintels or dressed stones can often be found that have already been reused several times.

What Brussels and Wallonia have in place

In Brussels, construction waste regulations are based on the Lansink ladder. Bruxelles Environnement states that this hierarchy prioritises the operations with the least environmental impact. Reuse ranks above recycling. Another obligation worth knowing about: a compliant inventory is mandatory for all demolition or renovation sites of more than 500 m² gross building area built before 1 October 1998. This refers to the asbestos inventory. It also has a bearing on reuse, since a contaminated material cannot be recovered.

Bruxelles Environnement also encourages a reuse inventory. It can be used, among other things, to tell the demolition contractor which elements need to be carefully dismantled. For public sector clients, a vademecum by Rotor sets out the approach and ready-to-use tools for extracting building materials from public buildings for reuse.

In Wallonia, the regional Circular Wallonia strategy has entered a new phase. The Walloon Government has identified four priority sectors: metals and critical raw materials, chemicals, construction, and agri-food/bio-based/water. In June 2026, the Boost4Circularity programme highlighted several flagship projects, including the development of a Walloon industrial sector for closed-loop recycling of flat glass from deconstruction and renovation, and a natural stone reuse project. The Service public de Wallonie (Walloon public service) also offers a platform listing reuse materials and techniques.

In our province, the BEP organised the 2nd edition of the Materials Exchange (Bourse aux matériaux, 10-11 April 2026), which allows stocks, surpluses and end-of-series items to find a new use.

Project examples where reuse makes sense

Reuse cannot simply be decreed. It depends on the existing building, the brief and the schedule. Here are three situations we regularly encounter.

Converting a farmhouse or barn into homes. This is the most natural territory for reuse:

• blue stone thresholds, frames or paving can be lifted out, cleaned and repositioned elsewhere in the project;
• natural slates in good condition can be sorted for an annexe or a secondary roof;
• sound timber roof beams can become lintels, staircases or fitted furniture;
• reclaimed old bricks allow an extension to connect without a visual break.

Converting offices into homes. Office buildings from the 1970s to 1990s contain many removable elements: internal doors, glazed partitions, raised floors, light fittings, sanitary ware, handrails. Some of these can stay in place, while the rest can go to the professional reuse sector. The Opalis directory lists just over 300 suppliers of reused materials, across a territory covering France, Belgium and the Netherlands.

Public projects and co-ownership buildings. Here, reuse is written into the specifications. Rotor published a guide in 2022 for formulating recovery targets within a works contract. On the structural side, Walloon initiatives such as the Alliance Réemploi Poutrelles (Beam Reuse Alliance) are working to structure the Walloon sector for reusing steel beams from deconstruction.

These approaches are gaining visibility. The Trophées Bâtiments Circulaires 2026 (Circular Buildings Awards) accepted projects located anywhere in Belgium, and this edition includes two Brussels projects among the entries. The winners will be announced at the awards ceremony on 26 November 2026.

The practical role of an architecture and engineering firm

Reuse is decided very early on, right from the sketch design stage. At our firm, it draws on several different disciplines.

• The survey. With BimBot, we scan the existing building in 3D, using drone footage and 360-degree photos. The model serves as the basis for the inventory: dimensions of elements, quantities, location. We know what we have before we start designing.
• Design. STARC's architects adapt the project to the available materials, rather than the other way round. The width of an opening can be set to match reclaimed window frames or doors.
• Structural stability. Reusing load-bearing elements (timber beams, steel sections, floor slabs) requires verification by Optibim's engineer: condition, cross-section, connections, loads carried.
• EPC (PEB) compliance. A reused window frame or insulation material must be documented. In the absence of reliable data, cautious default values often have to be used. This can affect the result. It is better to plan for it in advance.
• Scheduling. With Chronoplan, we build careful dismantling into the schedule. It takes longer than conventional demolition.

Pitfalls to avoid

• Forgetting the asbestos inventory. Without it, no serious reuse is possible.
• Deciding too late. Once a demolition contractor has been appointed without dismantling instructions, it is often already too late.
• Neglecting storage. Dismantled materials must be protected, labelled and stored somewhere dry.
• Underestimating labour. The material itself may cost less, but cleaning and reinstallation take time.
• Not including a clause in the specifications. The contractor needs to know what is expected, and how the reuse is guaranteed.

Do you have a building to convert, a farmhouse to repurpose or an office block to redevelop, and are you wondering what could be salvaged? Our teams at STARC and Optibim can carry out the survey, assess the reuse potential and integrate it into your project right from the first sketches. Get in touch with us in Gembloux to discuss it.