Souverain 23 is a residential complex located at Boulevard du Souverain 23 in Watermaal-Bosvoorde, on the edge of the Sonian Forest. The project was part of the redevelopment of the iconic Royal Belge site and was commissioned by Cores Development and Urbicoon (Woluwe). OSQB acted as the executive architect

The project entailed the realization of a large-scale multi-family residential building with 165 apartments and 5 commercial spaces, totaling approximately 13,500 m². The residential development was conceived as an ensemble of four residential building volumes, carefully positioned above an existing underground structure, with attention to scale, light, living quality, and the relationship with the green surroundings.

Sustainability formed an essential starting point within the project. In this context, the existing underground basement structure was retained down to level -4 and reused as a parking garage. This intervention significantly limited the material impact and allowed the existing load-bearing structure to be utilized to the maximum extent. The four residential blocks were subsequently constructed on top of this underground parking, enabling a well-considered combination of reuse and new construction.

As the executive architect, OSQB was responsible for the technical elaboration of the design, the preparation of the execution dossiers, and site supervision. A major challenge lay in carefully aligning the new above-ground volumes with the existing underground structure, from a structural, building physics, and technical perspective. Particular attention was paid to detailing, stability, acoustics, and energy performance, in accordance with applicable Brussels regulations and EPB standards.

The collaboration with the developers, engineering firms, and contractors proceeded in close dialogue, resulting in an efficient construction process and a high-quality end result. Through a consistent translation of the design intentions into feasible and sustainable solutions, a high level of living comfort was achieved, with attention to light, outdoor space, materials, and long-term value.

Souverain 23 today constitutes a significant residential addition to the Royal Belge site and illustrates how the reuse of existing structures, combined with contemporary architecture and technical expertise, can lead to a sustainable and future-oriented residential development. The project confirms OSQB’s role as a reliable partner for the execution of complex residential projects, where sustainability, technical precision, and construction quality are central.