A series of laboratory scale studies has been conducted to assess the thermal response of common rock types in Fennoscandinavia. The main objective of this experiment was to investigate experimentally the effect of initial compressive stress on thermal spalling and determine the mechanism causing thermal damage (spalling and fracturing) in rock observed in laboratory experiments. Seven tests were carried out including oven-dried and water-stored rock blocks, with and without applying bi-axial stress on three rock types, granite, gabbro and schist.