A structure is expected to remain for 30-300 years. Building services are most likely integrated into floors and wear out or become obsolete every 7-15 years (Brand, 1995). Currently, 58% of all timber products are landfilled (Lucas et al., 2017). To ensure timber structures’ long and useful service life, adaptability and integration with building services should be considered (Rogeau et al., 2021). A modular, adaptable shape, capable of integrating and replacing building services should be the outcome of this research. Many timber structures are expected to be built. Let’s prevent an environmental disaster of building waste in 2050 by answering the question: What disassembly and manufacturing improvements are necessary for timber floor systems to increase adaptability and circularity for building services in dwellings. The aspects to design a fully circular timber are circularity, manufacturing and structural. From the literature research, the following criteria are found that are related to these objectives: Modularity, Simplicity, Disassembly, Adaptability, Density and Slenderness. Summarized these objectives make: Easy Adaptive Reuse. A multi-criteria analysis (MCA) is used to grade the timber floor systems with the criteria found, the socalled grading tool. The outcome of the grading tool is a ribbed floor that can be disassembled into parts and connected by mechanical or shaped connections. The result is a final prototype by experimental design based on the criteria and improved through surveys. The final product is suitable for the construction industry and fits into mass customization to increase its impact. The engineering part uses the ribs for the ULS and SLS to shape a composite structure. By making a demountable mechanical connection the structure increases its circularity and stiffness, so it takes the best of both worlds. FlexHolz is a flexible system that increases circularity and is suitable for mass customization.