Water is the main vehicle of decay agents in Cultural Heritage building materials exposed to weathering. In this work, a simple method to produce superhydrophobic/oleophobic coatings building materials, including under outdoors conditions, has been developed. In addition, a study of the behavior of the developed coatings on different substrates (limestone, granite, concrete and wood) is reported. The addition of 40 nm-SiO2nanoparticles to a fluoroalkylsilane reduces surface energy and produces a Cassie-Baxter surface in all the materials evaluated. It promotes high static contact angle values of around 160°, and a contact angle hysteresis of around 3°, giving rise to repellence. The building surfaces also demonstrate an excellent self-cleaning performance. The coatings maintain the building materials esthetics as required in the Cultural Heritage field. Finally, the coating presents a long-lasting performance due to condensation reactions producing effective grafting to the four building materials evaluated.

Superhydrophobic surfaces present promising applications in the protection of building materials, such as the self-cleaning effect promoted by their high water-repellent properties. However, these surfaces easily lose their properties when exposed to oil contaminants. This is a critical weak point for their application in building facades, which are exposed to environmental pollutants such as hydrocarbons and vandalism (e.g., grafitti). A viable strategy to remove oils is to produce superhydrophilic surfaces, which present underwater superoleophobic behavior. In the case of buildings, the use of this strategy can be considered counterproductive because it promotes their interaction with water, the main vehicle of most decay agents. In this work, we have successfully combined the advantages of a superhydrophilic coating with a hydrophobic impregnation treatment, which prevents water ingress into the porous structure of the substrate. Specifically, a photoinduced superhydrophilic surface was produced on concrete by simple spraying of a starting sol containing TiO 2 NPs, which create a Cassie-Baxter state, a silica oligomer, producing a compatible matrix promoting good adhesion to the substrate and polydimethylsiloxane as a hydrophobic agent. After being exposed to sunlight, the treated surfaces switched from superhydrophobic (SCA 160°) to superhydrophilic (SCA < 10°). These surfaces presented underwater superoleophobicity (SCA 152°with CHCl 3 ) and oil-contaminated dust was easily cleaned without employing detergents. The photoactivation does not alter the protection against water absorption (>85% reduction). The treatment showed suitable adhesion to the substrate and good resistance to rainfall and outdoor exposure due to the presence of the hydrophobic silica matrix in the concrete pore structure.