[en] Measurements performed by the Institute during 2000 - 2013 are summarized. Focus was on ⁴⁰K, ²²⁶Ra and ²²⁸Th. Basic principles of the method of determination are explained, and an overview of the geologic sites from which building materials were extracted is presented. The results were related to the geologic structure type. Of the radionuclides examined, ⁴⁰K was found to contribute to the specific activity index I most. (orig.)