The influence of hydrophobic protection on building exterior claddings

This study presents the results of an experimental campaign with the aim of investigating the hydrophobic protection of three substrates (stone, render, and external thermal insulation composite system-ETICS) with the application of three hydrophobic products: silicon and titanium dioxides-based nanostructured dispersion (H-NST); a silane/oligomeric siloxane (H-Sila/Silox); and a siloxane (H-Silox). To determine the effectiveness of the hydrophobic treatments, specimens of the untreated and treated wall coatings were characterized with different laboratory tests. The results showed that all products introduced significant improvements in the hydric properties of the substrates, leading to lower capillary water absorption (98%), water permeability with Karsten pipes (99%), drying index (39%), and higher water repellency assessed through the contact angle (283%). The application of hydrophobic materials also had a negative effect, leading to up to a 227% increase in resistance to water vapor diffusion. Among the assessed wall coatings, the rendering mortar appears to have the best initial performance after the application of all the types of hydrophobic materials tested. In general, the hydrophobic product H-Silox was proved to be the most suitable for rendering mortars, while H-NST was more appropriate for stone substrates.