SYMPOSIA PAPER Published: 01 December 2022
STP164020210078

Long-Term Effects of Penetrating Water Repellents on Limestone

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Clear penetrating sealers and water repellents (primarily silanes and siloxanes) have been used as masonry treatments for decades. These products, sold as relatively low-cost, beneficial chemicals, claim to slow or prevent soiling and water absorption, thus reducing future maintenance. Studies regarding the short-term effect of these products on individual constituent masonry components are available, but the long-term impact of their application to building assemblies is not well documented. The Oklahoma State Capitol was treated with such products twice, once in the 1960s and again in the 1980s. The Topeka Municipal Building is known to have been treated in the 1990s and possibly once before. Both buildings exhibit shallow but consistent depth subflorescence-induced exfoliation of limestone (Indiana, Silverdale, and Kasota) in areas with moisture intrusion. The persistent but variable hydrophobic properties imparted to Indiana limestone at the Oklahoma State Capitol by the use of penetrating sealers contributed to soiling and staining that included alkali staining, which is a permanent disfigurement and which has complicated recent cleaning operations. These conditions arise from decades-old decisions to apply clear penetrating sealers. Although both case study buildings are faced with limestone, the observed long-term issues may affect other types of natural and manufactured masonry. The condition of the exterior envelope of a building, both at the time of application and in the future, affects the performance of such sealers. Because it is not possible to remove penetrating sealers and water repellents, the potential for long-term harm should be carefully considered before deciding to apply them. This paper describes the factors that should be considered.

Author Information

Manglitz, Julia, E. Mathias
TreanorHL, Topeka, KS, US
Kelley, Kenneth, V.
TreanorHL, Topeka, KS, US
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Pages: 244–263
DOI: 10.1520/STP164020210078
ISBN-EB: 978-0-8031-7728-4
ISBN-13: 978-0-8031-7727-7