Architect: Bureau Bouwtechniek
Client: Toyota Motor Europe NV/SA
Surface: 79.265 m²
Budget: € 4.389.310
Timing: 2024 -
Status: In execution
Advisors: Bertram (stability)
For this project, we carried out a thorough technical survey of the existing roof structure and the general condition of the flat roof. Based on this analysis, it was decided to completely remove the existing roof waterproofing, insulation and vapour barrier and replace them with a new, high-performance roof structure. The supporting structure was retained.
The renovation is being carried out in phases: work on phase 1 has started on the roof of WH-03a.
Phase 2 will start in September 2026.
The inspection revealed that the existing roof structure no longer met current energy and building physics requirements. Consequently, a lightweight roof structure was chosen, tailored to the load-bearing capacity of the existing substructure and validated in consultation with the structural engineer.
The new insulation package was dimensioned to achieve a U-value of 0.20 W/m²K. This ensures the roof meets current EPB requirements and significantly improves the building’s thermal comfort and energy performance. Particular attention was paid to the detailing of the connections – at roof edges, upstands and penetrations – to avoid thermal bridges and the risk of condensation.
The roof houses a considerable number of technical installations: solar panels, air handling units, cable penetrations, vent pipes, skylights, rooflights, safety lines and lightning conductors.
These installations were dismantled prior to construction. Following completion of the new roof structure, they will be reinstalled and, where necessary, replaced.
A key consideration in the design was the upstand height of these installations. Most existing roof upstands proved to be adequate in principle, but given the increase in insulation thickness, a local verification is necessary. Specific bases that do not meet the required minimum upstand height will be modified to prevent water infiltration and splashing rainwater. In this way, we guarantee a durable and watertight connection in the long term.
The raising of the roof structure also affects the rainwater drainage system. The existing system consists of PE pipes operating under negative pressure (a siphon system), with emergency drains that discharge above the roof covering and are routed internally to the other side of the building via penetrations in the external façade.
Depending on the new insulation thickness, both the regular rainwater drains and the emergency drains will be modified. This involves checking whether the inlet heights, emergency overflows and penetrations continue to function correctly within the revised level of the roof structure. In this way, safety during extreme rainfall remains guaranteed.
The project also examined the extent to which an FM Approved roof structure was relevant or required for this project. This assessment formed part of the broader technical evaluation of the roof structure and the risk assessment.
From Team Renovation, Restoration & Maintenance (2)
