A major renovation in the heart of the city

The courtyard of the Serclaes Building is situated on a roof structure above a restaurant and an underground car park. The existing roof structure had structural defects in its waterproofing, resulting in water ingress and consequential damage to the spaces below.

The contract involved the complete dismantling of the existing structure and the construction of a new, technically advanced warm roof system, combined with a sustainable terrace finish.

Maintaining the continuity of functions beneath the roof required a phased and controlled execution.

The aim: to combine a sustainable roof structure with a high-quality, multifunctional outdoor space that can once again be used extensively by students and visitors.

Logistics and execution within a compact building block

The site was situated within a densely built-up block, with no space available for site facilities on public land. Access to the roof area was via a covered passageway approximately 4 m wide and an adjoining walkway.

The use of heavy machinery was out of the question. The demolition of the substrate, concrete elements and existing roof layers was carried out entirely by hand. The delivery and removal of materials was organised via a meticulously planned logistics plan, with phased deliveries and minimal storage on site.

This context required extensive coordination between the design team, contractor and suppliers, with continuous alignment of planning and execution.

Dismantling and ground analysis

Following the removal of the existing roof layers, the supporting structure was subjected to a destructive inspection. Connection details at upstands, penetrations and drainage outlets were re-evaluated.

The existing slopes were re-measured digitally and manually. This survey formed the basis for redrawing the drainage plan. This allowed the original slope gradient towards the existing drain outlets to be retained, without the need for additional slope insulation.

A verification calculation confirmed that the number and dimensions of the drain outlets were sufficient for the entire roof area.

The project also provides for the possibility of connecting the rainwater to a reuse system in the future, without requiring any further work on the roof waterproofing.

Warm roof construction and thermal continuity

The refurbished roof structure was constructed as a traditional warm-roof system:

bituminous vapour barrier, airtight connection to vertical upstands
120 mm PIR insulation, installed using an adhesive
two-layer bituminous roof waterproofing

Particular attention was paid to:

continuity of the vapour barrier at upstands and penetrations
correct upstand heights in accordance with applicable guidelines
thermal break at connections with existing façades
stress-free connection around structural penetrations

The design details were adapted to the limited construction heights available at the edges, without compromising the required flood defence heights.

Local reinforcement and future loads

With a view to the possible future installation of green areas or heavy elements, specific areas were fitted with compression-resistant insulation (foam glass).

This insulation was installed loose within the ‘trough’ formed by the bonded PIR system. This choice is technically justified:

stable positioning without additional bonding
avoidance of stress build-up in the roof structure
reversibility for future modifications

Thanks to these local reinforcements, the roof structure is prepared for higher point and line loads, without impacting overall thermal performance.

Paving with variable installation heights

The Dreen® Ceramica tile system from Zoontjens (colour: Flux Concrete) was chosen as the final finish, installed using the DNS® system.

The existing supporting structure exhibited significant differences in height. The available installation height varied from approx. 35 mm to several decimetres. At the same time, the entire square had to be fully wheelchair accessible, with minimal differences in level.

In collaboration with the supplier, a detailed installation plan was drawn up in advance. The terrace construction was technically adapted to the available height for each zone, whereby:

the system was modularly adapted to varying heights
connections to steps, columns and curves were precisely fitted
the cutting work was coordinated in advance to control tolerances

The result is a flat, water-permeable and removable terrace surface that allows the underlying roof waterproofing to be inspected.

Tight construction schedule

The complete renovation – dismantling, reconstruction and finishing of 815 m² of roof area – was carried out within a strict timeframe from June to September 2024.

The project was completed in time for the start of the academic year, with a focus on both technical performance and user comfort.

our experts

From Team Renovation, Restoration & Maintenance (2)

ir. arch. Alexander Scheepers

Project architect

E-mail |

arch. ass. Tuur Van Dijck

Advisor flat roofs
Safety coordinator

E-mail |

references

Campus VUB Etterbeek

Etterbeek

Commissioned by the Vrije Universiteit Brussel, we are supervising the major renovation of the roof of building R, which houses the restaurant and cafeteria of the Etterbeek campus.

Middelheim hospital

Antwerp

Renovation and repair of the access areas of Middelheim general hospital.

Odisee Campus