Traditionally stone architecture has been built in the Dhofar region in Southern Oman. However, modernization policies under the reign of Sultan Qaboos since the 1970s have led to the replacement of traditional building materials with industrial ones. As research on the manufacturing methods and usage of traditional materials is limited, many buildings are at risk of disappearing. This study aims to clarify the functions and properties of the three principal materials, khatri, nurah, and yeb', used as both joint and finishing materials in the coastal areas of Dhofar. According to interviews with local traditional masons, khatri is used as a joint and wall-finishing material, nurah as a wall-finishing material, and yeb' as a floor-finishing material. Particle-size tests revealed that the particles become finer in the order of: khatri, nurah, and yeb'. Furthermore, XRF and XRD reveal that nurah had a higher calcium content compared to khatri and yeb'. The combination of interviews and engineering experiments indicate that the manner in which local masons use these three materials is highly dependent on their physical properties. This can be reasonably explained based on the climate: Dhofar experiences more rainfall than Northern Oman during summers. These findings can aid in the improvement and continuous use of traditional building materials and contribute to a sustainability.