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Ensuring Moisture Protection for Manufactured Stone Drainage and drying for absorptive claddings by Jeff Diqui, Arch. Eng., CSI All images courtesy Sto Corp. FAILURES OF CLADDINGS LIKE ADHERED MASONRY VENEER–ALSO KNOWN AS MANUFACTURED STONE–OFTEN STEM FROM POOR FLASHINGS, MISAPPLIED AIR AND WATER-RESISTIVE BARRIERS (WRB S ), AND LIMITED DRAINAGE. RESULTING PROBLEMS RELATED TO MOISTURE INTRUSION INTO THE WALL ASSEMBLY’S DRY ZONE ARE MOIST WALL INTERIORS, WET INSULATION, AND ROT IN SHEATHING AND FRAMING. Experience has shown detailing flaws in cast-stone veneer causes leaks which can lead to severe damage inside the wall. Rain and wind are often the culprits. A related effect in adhered masonry veneer cladding is inward vapor drive, which can occur in warm weather. It forces moisture stored in the masonry through vapor-permeable housewraps and building papers and into the sheathing and stud bay. This can lead to condensation and water accumulation within walls, as well as wood decay and condensation on interior surfaces. 1 Some have assumed WRBs between claddings and sheathing layers prevent moisture damage. Research and field experience demonstrate the WRB alone may not always suffice. 2 Common practices, such as using double layers of housewraps or asphalt- impregnated papers behind the absorptive claddings, are shown to be ineffective under some climate and weather conditions, particularly if poorly constructed details allow excess water into walls. 12 the construction specifier | january 2013 CS_Jan2013.indd 12 12/12/12 9:32:37 AM