In the present work, a novel polymeric coating for mortars protection was prepared via free radical polymerization between methyl methacrylate (MMA) and stearyl methacrylate (STEA) to overcome the well-known technical problems related to the use of commercial Polyacrylic protectives. The physico-chemical properties of MMA_STEA and the effect of different STEA amounts (1.0-2.5-5.0% mol/mol respect to MMA) on MMA_STEA features were determined via H-1 NMR and FT-IR spectroscopy, Gel Permeation Chromatography (GPC) and Differential Scanning Calorimetry (DSC). Furthermore, the long-term behavior of these polymeric protective agents was evaluated by means of accelerated aging tests exploiting UV radiations. MMA_STEA coatings were applied to air-hardening calcic lime mortars and their performances were studied using different surface techniques: static water contact angles (WCAs), CIELab colorimetric tests, water absorption by capillarity and water vapour permeability (WVP). All measurements were also performed after an UV aging test to study the durability of the coatings applied on mortar. This work demonstrates that a polymer coating prepared starting from methyl and stearyl methacrylates-based comonomers is an efficient way to obtain mortar protectives with satisfactory water repellent behavior, transparency and durability.