Is the assessment of cementitious adhesive for ETICS based on the adhesion strength tests always reliable and rational?

The article presents the results of an interlaboratory comparison [ILC] of determining the adhesion strength of the cementitious adhesive, which is a component of ETICS to the concrete substrate and the thermal insulation material - EPS board. Seventeen laboratories belonging to ETICS manufacturers or suppliers of raw materials for the production of ETICS participated in the ILC, organized by the Polish Association for ETICS. The determined values of the standard deviation of repeatability sr in the range from 9.73 % to 14.37 % and the standard deviation of reproducibility sR in the range from 22.67 % to 44.36 % of the determination of the adhesion strength of the cementitious adhesive to the concrete substrate and the value of the standard deviation of repeatability sr in the range from 8.29 % to 17.50 % and the standard deviation of reproducibility sR in the range from 17.82 % to 30.17 % of the determination of the adhesion strength of the cementitious adhesive to the EPS board in various storage conditions of the test samples indicate that the tested method is characterized by low precision. It means that the assessment of compliance with the test results obtained by this method with the acceptance criteria when different laboratories perform measurements may be divergent, and the risk of incorrect assessments is high.