This study tests the impact of using a chemical damp-proof cream, containing mainly silanes and siloxanes, on disrupting the damp rising in mortars. The test is performed on mortar specimens using a mercury porosimetry, a contact angle tester and a thermographic camera. Based on the test, the differential pore volume distribution and content of ink-bottle shape pores were defined, areas of apparently different hydrophobicity were indicated and the maximum distances of the chemical injections were set. The results show that the chemical damp-proof cream has a significant influence on the hydrophobicity and microstructure.