Adhesion of mortars is a complex mechanism that is affected by several in-service factors. Numerical modeling complements adhesion lab tests because it allows a high number of case studies in a reduced period of time and with few resources. In this paper, an interface layer with a constitutive cohesive zone model is introduced to simulate the adhesion loss between mortar and substrate. A parametric analysis is performed to study the sensitivity of the relevant parameters of the model and two application examples are presented. The numerical applications show that the proposed model can reproduce in-service factors that influence the adherence.