Despite growing interest in natural fibers for sustainable construction, few studies systematically integrate empirical mechanical testing of Andean biomaterials—such as totora (Schoenoplectus californicus)—with parametric design to enhance structural performance. Historically limited to non-structural applications, totora’s potential in load-bearing systems remains underexplored. This study addresses this gap by evaluating and optimizing totora-based modular units through a hybrid methodology that combines traditional weaving techniques, physical testing, and computational simulation. Cylindrical and conical modules, fabricated using cross-weaving and spiral braiding, were subjected to tensile and compressive load tests. Concurrently, ephemeral structures composed of these modules were developed in Rhinoceros using Grasshopper/Karamba3D to explore geometry optimization and load response, iteratively refining morphologies based on stress distribution patterns. Results demonstrate that conical forms and spiral configurations significantly improve stiffness and load dissipation, while all modules exhibited high ductility and full shape recovery after compression. The study confirms that parametric design can effectively compensate for totora’s inherently low strength by adapting form to material behavior. This approach offers a replicable framework for integrating vernacular knowledge with digital tools in sustainable, ephemeral architecture across Andean contexts.