Abstract: Existence of cavities and weak zones on gypsum was explored in a boarding school property by using direct current resistivity, ground penetrating radar and seismic refraction methods. Twodimensional inversion of the direct current resistivity data and evaluation of other methods pinpoint eight cavities and two weak zones as well as their possible interconnections. The drillings at selected locations confirmed the existence of these cavities nearby or extending underneath the buildings at the depths of 1 m to 7.50 m.