The most commonly used wall coverings are still, undoubtedly, plasters and renders, whether lime-based or cement-based, whether traditional and prepared in-situ or pre-dosed. In accordance with the available standards, the characterization of these mortars is made on laboratory test specimens, with dimensions, curing conditions and test procedures according to the prescribed. However, when applying these mortars to the real substrates, their behaviour will not be the same. After application of the mortar to the substrate, an interface will be formed, and the interactions that occur after the contact of the mortar, still in the plastic state, with the substrate will change over time due to the hydration kinetics and absorption of the substrate. It is very important to know the real behaviour of mortars after application, in order to ensure their durability. A research project is being developed to analyse the proper behaviour of mortars after application to the substrates. In order to characterize a mortar after application to a substrate, it is necessary to detach it. The introduction of a fiberglass grid in the mortarsubstrate interface makes the detachment easier. The purpose of this study is to determine if the placement of this grid will influence the characteristics of the applied mortar. For this, an experimental campaign was carried out, comparing the characteristics of two mortar formulations, applied to different types of substrate (without introduction of the fiberglass grid), with the characteristics of these mortars applied to the same substrates, but with the introduction of a fiberglass grid at the interface mortar-substrate. In this paper, we present the results obtained for some of the physical and mechanical characteristics of cement and hydraulic lime mortars.