Damages due to fre occurred on many monuments and afected building sandstones. Changes in technical properties of
heated sandstones are caused by changes in their structure and mineralogy. Therefore, a better knowledge of the changing
processes in grain size scale is crucial to understand and assess property changes. The study presents results for the Cotta type
Elbe Sandstone, a clay-bearing sandstone that is a widespread material for construction and sculpting. Uniaxial compressive
strength and ultrasonic wave velocity as well as changes in colour, structures and mineralogical phases were determined for
samples treated at temperatures of 300, 400, 500, 600, 700, 800 and 1250 °C and compared to the untreated material. The
results show that minor clay components in the sandstone pores determine the uniaxial compressive strength in dependence of
temperature and dry or wet state. Uniaxial compressive strength does not show a decrease even at high temperatures, whereas
ultrasonic wave velocity is decreasing continuously with higher temperatures as for many other sandstones. The difering
mechanical behaviour of the clay-bearing sandstone can be explained by the phase changes of kaolinite in the pore cement.