The sandwich construction of the roof module's support structure delivers good flexural strength and dimensional stability. It is made up of two glass fibre mats with a lightweight core layer between them - a polycarbonate or paper honeycomb, for example. The mats and the core layer are bonded to the Baypreg polyurethane system from BaySystems by compression moulding. At the edges of the roof, the sandwich construction's support function is taken over by the Baypreg polyurethane spray system, which is processed in solid form and reinforced with long glass fibres. The solid area at the edges is used to create a bond to the roof frame of the bodywork. It is also easy to integrate inserts such as handles, and the entire roof module is able to withstand even higher mechanical loads. Working outward, the support structure is followed by a multifunctional intermediate layer of the highly reactive two-component polyurethane system Multitec. This prevents glass fibres or cavities from appearing on the roof surface. The material's beneficial properties include very low linear expansion and high tensile strength. It also ensures good adhesion between the support structure and the coated Makrofol polycarbonate film forming the roof's surface.