Restoration of sandwich panels in architectural heritage

Sandwich panels are a building system that consists of an outer skin, a core and an inner skin. Architects have used sandwich panels to create a high-tech or industrial appearance, for example in the Sainsbury Centre for Visual Arts (1978, Norwich) by Norman Foster. Restoration of this construction system is important for safeguarding these buildings. The sandwich panel was developed by Jean Prouvé around the Second World War. The panels have been produced on a commercial scale since the 1960s. Initially, sandwich panels were produced using steel skins, but later also materials like aluminium, glass-reinforced polyester, PVC, asbestos and precast concrete were used. The thin skins and critical detailing make sandwich panels vulnerable to decay. Buildings from the 1960s to the 1980s are now reaching the end of their technical lifespan. Research on the restoration of the construction systems that built them is necessary for preserving them for future generations. Sandwich panels are threatened by various types of decay, depending on the material, the context and the detailing of the panels. Conservation interventions are often possible, but some decay is irreversible. The preservation strategies for the various materials are discussed and evaluated. Additionally, the restorations of four buildings employing sandwich panels are discussed in more detail. Although all use sandwich panels in their façades, the interventions vary significantly. In the projects analysed, the design of the restorations varies in level of conservativeness. The interventions performed reflect the extent of the decay, the proposed function of a building and the legal protections surrounding the work. A deep understanding of the history, a thorough study of the material and a critical analysis of several case studies will illuminate the significance of sandwich panels in architectural heritage and guide the technical approach for the restoration of this remarkable construction system.