This paper reports on the design and construction of a lightweight GFRP roof structure in Basel, Switzerland. The sandwich construction allowed for an integration of static, building physical and architectural functions that enabled the prefabrication of the entire roof in only four lightweight elements that were easily transported to the site and rapidly installed. Cutting of foam blocks with a computerized numerical control machine and adhesive bonding proved to be advantageous procedures for the fabrication of the complex roof shape, without the use of expensive moulds. The applied design methods were validated through small- and full-scale experiments. The safety level of the design was adjusted during the design process through experimental verification. Although some of the characteristic material properties were overestimated in the preliminary design, the design properties for the final design were higher than for the preliminary design since it was possible to reduce the resistance factors after testing by a factor of 2.0.