I am building a structure with Single Wythe CMU walls. Do I need flashing and a water repellent coating?
A. Concrete block, particularly lightweight concrete block, is not weather tight if you do not apply a water repellent coating to it. Water repellent coatings usually last between 2 and 10 years, depending upon the exposure of the building and the competence of the applicator. As a rule of thumb, penetrating water repellents last longer because they are not as prone to ultraviolet degradation as surface coatings are. I recommend Silane and Siloxane-based coatings because of this longevity. If you want to read more about water repellent coatings for concrete block, go to the web site for the National Concrete Masonry Association at HYPERLINK “http://www.ncma.org/” www.ncma.org. Look for an icon labeled “E-Tek”. Click on this heading and it will take you to another web site where you can download technical articles.
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- I am building a structure with Single Wythe CMU walls. Do I need flashing and a water repellent coating?
