The influence of hydrophobic protection on building exterior claddings

  • Carlos Esteves
  • Hawreen Ahmed
  • Inês Flores-ColenEmail author
  • Rosário Veiga


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 (HNST); a silane/oligomeric siloxane (HSila/Silox); and a siloxane (HSilox). 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 HSilox was proved to be the most suitable for rendering mortars, while HNST was more appropriate for stone substrates.


Rendering mortars External thermal insulation composite system Stone Silicon-based hydrophobic product Superficial protection 



Acknowledgments to CERIS research unit from IST, REuSE project from LNEC, refª 0803/112/19461, and WGB Shield project from FCT, refª PTDC/ECI-EGC/30681/2017. The authors wish to thank Dr. Dória Costa, Dr. Lina Nunes from National Laboratory for Civil Engineering (LNEC) for performing the contact angle and biological colonization tests, respectively, and Eng. Sofia Malanho and the technicians for their support in the experimental work from LNEC. The authors acknowledge Weber, NanoPhos, and CIN manufacturers for the hydrophobic products.


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Copyright information

© American Coatings Association 2019

Authors and Affiliations

  1. 1.CERIS, DECivil, Instituto Superior Técnico, Universidade de LisboaLisbonPortugal
  2. 2.Laboratório Nacional de Engenharia CivilLisbonPortugal

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