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APTNW Technical Workshop

The NW Chapter of the Association of Preservation Technology is organizing a workshop on water repellents to be held in Seattle on April 29th.  The use of water repellents on historic masonry can be a divisive topic.  Knowledgeable professionals who generally abide by the same preservation tenets often confront a difference of opinion on the use of water repellent systems on historic buildings.  One school of thought encourages the use of water repellents as a means to improve material performance and protect the envelope from moisture intrusion; another school of thought posits that water repellents will alter water vapor transmission systems that have been in place for decades, introducing the potential for deleterious short- and long-term effects. The goal of this workshop is to engender a lively discussion of water repellent systems by dispelling misconceptions, educating participants on the science of water repellency, and sharing case studies of historic masonry buildings with and without water repellent interventions. Registration for the Water Repellant Workshop can be found here,, or at the APTNW Website,