One of the sources of heat loss in the building is the joints of the windows and the doors with the wall. The article presents the problemof correct thermal insulation of window and door joinery in the ETICS layer. Based on many years of expert experience, some reasons for the occurrence of thermal bridges at the joint of the „frame-wall” have been presented. Keywords: installation of windows and external doors; thermal insulation; External Thermal Insulation Composite Systems (ETICS).