The physical deterioration of concrete structures is mainly caused by their moisture content. Consequently, methods dedicated to contactless, non-destructive and real-time monitoring of moisture content levels are required to control the deterioration of buildings. In this study, we propose an instrument integrating the hardware and software resources suited for the evaluation of the moisture content according to these requirements. The technique proposed is based on the measurement versus time of the reflection coefficient of a moist sample by means of a monostatic radar build up with a home-made network analyzer connected to a horn antenna. Experiments are conducted at the test frequency of 2.45 GHz to determine the concrete moisture content.