In order to welcome translator interpreters to Solbosch, the ULB is organizing at the end of 2018 a design and construction competition aimed at the extension of the U Building, which is won by A2RC in partnership with Valens. The project respects the formal symmetry underlying the design of the U building, which gives the site its structural strength, by reproducing - discreetly adapted to the presence of the extension facade of technical hoppers - the adjoining extension made by A2RC for ISA Victor Horta. Emphasis is placed on the center of the building, which emphasizes the axis of symmetry, and a discreet dialogue with the tower of the iconic Solbosch building. Both a connecting bridge between the different faculties hosted and a discreet crowning of the building, it takes its rhythm in a work of frames and panels applied in shadow boxes, hiding the important technical installations required by the chemistry laboratories. The project brings together classrooms and language laboratories along the exterior facades, thus taking advantage of the light and the views. The distribution corridors run alongside the interior courtyards, the view of which favors spatial orientation. The areas assigned to teachers and researchers occupy the separate wing, away from the classroom, for reasons of peace of mind for research work. A multipurpose room provides the link between these two groups. Lastly, the program offered specific technical challenges: rapid construction, respecting ULB's environmental commitments and allowing laboratory equipment to be kept in operation during the work. The project responds by choosing a modular wooden construction, enlargement pre-assembled in the workshop, and offers an exemplary construction in terms of sustainability. The glued laminated structure allows rapid assembly, which not only provides protection against the rain, but even more timely enhancement of the various extractors of the chemical laboratories, in a fully coordinated way between the requirements of the site and those of the occupants.