Moisture significantly affects the structural integrity of buildings, particularly in earthen materials, where its presence in vapor and liquid forms drives degradation processes. These materials, often termed “breathing” due to their porous structure and exceptional hygroscopic capacity, are increasingly relevant to sustainable construction. This study advances material development workflows for earth-based 3D Printing by investigating the dimensional response of a soil sample to temperature and moisture variations. An experimental campaign utilized a controlled climatic chamber with an average temperature of 25 °C and relative humidity of 64%, where earth material specimens, monitored with displacement sensors, underwent hygroscopic testing to determine the dimensional variation in two directions, radial and tangential. The results showed that the selected soil sample exhibited adequate dimensional stability, with a maximum variation of only 0.15 mm, significantly lower than the oak samples, which expanded by up to 1 mm. Despite this stability, cracking was observed, indicating potential challenges for durability. These findings highlight the promise of earthen materials for achieving precise geometry control in 3D-printed structures, offering valuable insights into optimizing sustainable construction technologies while underscoring the need for further refinement to mitigate cracking.