This study characterizes the thermal, chemical, mineralogical, and microstructural properties of the materials in a historic building. The case walls, located in the historic hub of Karachi, Pakistan, are almost 100 years old and in danger of losing their originality due to the deterioration of the materials. Eleven locations are identified with the help of a thermograph analyzer, and samples consisting of stone, mortar, and plaster are collected for characterization. The analysis is carried out by employing X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). Either calcite or calcium carbonate is found in large quantities in all samples, along with quartz, which is found in significant quantities in the mortar and plaster. The identification of quartz reveals the presence of aggregates in mortar and plaster binder. Moreover, the chemical characterization identifies samples as lime mortar and plaster with high and moderate hydraulicity. Similar results are reported through XRD and TGA, with additional findings of gypsum and portlandite. The appearance of the latter-mentioned minerals, along with calcite, dolomite, feldspar, brucite, and quartz, are verified through microstructural characterization. Moreover, using SEM images, the aggregate size is evaluated, with the presence of medium-to-coarse sand identified in the mortar, and fine-to-medium sand found in plaster. A binder to aggregates was estimated as 1:2.5 for mortar and 1:4.5 for plaster through CaCO₃/ SiO₂ ratio.