The durability of mortar coatings is directly linked to their permeability. Crystallization additives have the potential to modify the pore structure and connectivity within the mortar, thereby improving its permeability. These additives serve the dual function of preventing water ingress while allowing water vapor permeability, which is crucial to promote moisture elimination in mortars. This study aims to analyze the effectiveness of a crystallization additive in enhancing the water vapor permeability of mortars. For this evaluation, samples with proportions of 1:1 and 1:3 (cement: sand, dry materials, by volume, produced by weight) were prepared with the addition of 0%, 1%, and 3% crystallizer based on the cement mass. These proportions were evaluated over time in both the fresh and hardened states, following the Portuguese standard NP EN 1015-19 for determining the water vapor permeability of hardened plastering mortars. Scanning electron microscope (SEM) images were also captured. During the fresh state, the addition of 3% crystallizer impacted the workability of the mortars. However, through rigorous statistical analysis, it was determined that the incorporation of the crystallizing additive in the mortar did not significantly affect its steam permeability. As a result, the additive effectively prevents water from infiltrating and filling the pores of the material. The SEM images depicted the presence of potential crystal formations in the 1:3 mortar mixture containing 3% additive, which underwent wet curing (WC) for 97 days. Moreover, the observed crystallization process facilitated the ability to self-heal a crack, with Energy dispersive spectroscopy (EDS) analysis revealing a predominance of calcium hydroxide particles (Ca(OH)₂). This behavior demonstrates the viability of incorporating this particular additive in coating mortars, introducing a novel approach to these construction systems.

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