To reduce resource consumption and the carbon footprint of the construction industry, new construction principles that stipulate the minimisation of materials are urgently needed. Floor slabs show high potential for saving materials and CO₂ emissions, as they account for around 50% of the total volume of concrete used worldwide. A promising approach is the use of corrosion-resistant carbon fibre-reinforced polymer (CFRP) reinforcement, which requires only a small concrete cover to meet bond requirements. Regarding the component’s topology, material-efficient ribbed or waffle slabs have been built for decades but their execution has declined owing to their labour-intense production, which calls for manual installation of the formwork. A recently proposed extrusion manufacturing process combines both approaches for material-minimised construction and allows the fast and formwork-free production of carbon reinforced concrete (CRC) components. This article describes the concept, the finding of the form, fabrication and experimental testing of an innovative ribbed floor slab composed of precast extruded carbon reinforced concrete (ExCRC) webs. The novel floor slab consists of a conventionally cast thin-walled top slab and shaped, load-adapted ExCRC webs to achieve high utilisaton of the structural member. The ribbed slab provides a lightweight structural system with drastic savings in dead load compared with a conventional steel reinforced slab. In addition, the high durability and service life of the novel floor slabs makes them ideal components to be recovered after an initial life cycle and to be re-used in new construction projects. The paper gives an outlook to the full-scale production of one-way and two-way slab systems made of ExCRC such as ribbed slabs, waffle slabs and sandwich slabs with a honeycomb infill.