The work presented here is one of the fundamental phases of a research programme on seismic evaluation of existing buildings, funded by the Department of Civil Protection and developed at the European Centre for Training and Research in Earthquake Engineering (Eucentre). The present article contains a brief summary of the general theory on scaling: this concepts are then specialised for RC structures to be tested on shaking tables. These ideas are finally applied to the numerical model of the studied building and actually under testing on the Eucentre shaking table.