Soil, as a locally sourced and low-carbon material, has been shown to have considerable potential for use in sustainable construction, particularly when adapted for use with advanced 3D printing technologies. Current research has demonstrated the potential of integrating soil with additive manufacturing(AM) to create environmentally friendly and structurally robust materials. However, there are still core issues to overcome in understanding the physical and mechanical properties of 3D-printed soil and optimising its performance for practical applications. A central focus of this research is the detailed characterisation of soil materials sourced from the Valldaura region, conducted in collaboration with the Institute for Advanced Architecture of Catalonia (IAAC). In this work, physical and mechanical characterisation techniques, including granulometric analysis, sedimentation tests, Atterberg limits, methylene blue, X-ray fluorescence (XRF), X-ray diffraction (XRD) and compressive strength evaluations, were applied to comprehensively assess the properties of 3D-printed soil prototypes. Results revealed that the optimised soil mixtures achieved compressive strengths of up to 2.16 MPa and exhibited enhanced static modulus of elasticity (MOE) (up to 1.99 MPa) compared to traditional moulded soil samples. Lower plasticity indices and improved granulometry contributed to better workability and dimensional stability, while the XRF and XRD analyses highlighted the high silica content (47.98%) and the presence of quartz and orthoclase, which provided strength and stability to the mixtures. These factors collectively enhanced the soil's suitability for 3D printing applications. These findings underscore the viability of 3D-printed soil as a sustainable material for modern construction. Future research should focus on refining printing techniques, exploring the incorporation of supplementary additives, and conducting long-term performance assessments under diverse environmental and load conditions. This study provides a foundation for advancing the application of soil-based 3D printing technologies, contributing to innovative, adaptive, and eco-friendly building solutions.