The original roof structure was plagued by structural water infiltration problems and severe concrete damage. A total renovation focusing on waterproofing, thermal performance and preservation of the building's brutalist character was inevitable.

At the start

The roof of building R on the VUB campus is constructed from a grid structure of concrete beams. Within this grid are raised roof elements filled with skylights and light domes. The roof structure was designed based on an inverted beam layout, creating a series of recessed zones, known as bakzones. Rainwater was drained internally via overflows between these zones through pipes embedded in the concrete structure. This construction was originally part of a green roof concept: the box zones were to be filled and planted.

Water infiltration

Due to recurring problems with water infiltration, a thorough renovation of the roof is necessary. The internal drainage system will be abandoned: from now on, water will be directed above ground via the roof parapets to the facades. This requires complete dismantling of the existing roof structure, followed by filling the trough areas to create a single flat roof level. A new roof structure will be installed on this surface with sloped insulation to ensure efficient water drainage to the façade.

Interventions

Filling in the container areas will require additional interventions. The roof parapets will be raised and fitted with spouts. The connections with the curtain walls will also need to be adjusted to the new roof level. The existing joinery of the skylights is technically outdated and will be replaced in its entirety. The correct height of the upstands will be respected in relation to the raised roof level. The renovation will be completed with the installation of an extensive green roof, in accordance with the original design concept.

Complexity & challenges

The renovation involved a series of radical and technically demanding choices:

Concrete damage repair: Instead of local concrete repairs, we opted for a uniform approach in which all damaged concrete drip edges were milled off along their entire length. The reinforcement was treated with a corrosion-resistant coating, and the whole was finished with a new wall cap as part of the renewed joinery.
Redesigning drainage: The internal drainage system was abandoned. To divert the water to the facades, all lowered tray areas had to be levelled out. This was done with steel deck constructions, on which a new roof structure with sloping insulation could be installed.
Raising the roof surface: The addition of insulation and a green roof structure created a higher roof level, which required interventions to the upstands, connections with curtain walls and detailing to the joinery. The new concrete upstands were aesthetically integrated with wooden formwork boards, in line with the brutalist façade.
Replacement of skylights: The existing wooden skylights were technically and aesthetically inadequate. They were replaced by high-performance aluminium curtain wall profiles with adapted glazing. An opaque film was applied to the highest areas to prevent direct view from surrounding buildings.
Phasing & continuity of use: The work was carried out in phases to allow the student restaurant below to remain in use. This required careful planning of temporary coverings and phased replacement of joinery, with an eye to safety, hygiene and comfort.