The Royal Museum for Central Africa in Tervuren was built in the beginning of the 20th century. The outer walls and ornamental elements were almost exclusively constructed in massive blocks of Luxembourg sandstone, a stone well suited as building material. Despite the stated good quality, the facades locally suffer from exposure to weathering. Moreover, certain zones show severe damage due to rain water infiltration originating from defects in the water evacuation system which is entirely hidden within the walls. As a consequence, important damage to the sandstone blocks in the form of crack-formation, scaling, spalling and (salt) staining, is noticed. This paper presents the results of an investigation carried out in the framework of the restoration strategy aiming to explain degradation and damage phenomena in relation to the properties and varieties of Luxembourg sandstone. Detailed visual observations with regard to the architectural concept was followed by a sampling plan and a test program. Physical and microscopic analysis allowed to establish the relationship between rock type, colour and weathering effects. The test program consisted of the determination of physical and mineralogical properties, hardness profiles obtained by means of the portable DRMS device (Drilling Resistance Measurement System), ultrasound velocity measurements and the determination of the actual salt contamination. The strengthening effect of a number of consolidation tests, using tetraethoxysilane (TEOS), was also evaluated by means of hardness profiles.