This paper proposes the application of optimization techniques to design reticular structures made from a stock of reused elements. Still little explored, the reuse of structural components over multiple service lives has the potential to reduce the environmental impact of building structures. Construction based on reuse avoids sourcing new material, reduces superfluous waste, and requires little energy. However, designing a structure from a stock of reclaimed elements entails a change of paradigm. In contrast to conventional design practice, the structure geometry and topology depends on element stock characteristics, e.g. available cross sections and lengths. This paper extends discrete structural optimization formulations to assign stock elements to truss systems. An iterative approach is proposed: 1) element assignment and topology optimization are first carried out; 2) geometry optimization follows thereafter to improve the system geometry to reduce cut-off waste for assigned stock elements. Two case studies are presented to validate the proposed design method and to quantify environmental impact reductions of structures made from reused elements.