The introduction of architectural block has dramatically improved the appearance of concrete masonry walls. But eliminating traditional waterproofing surface treatments can lead to excess moisture absorption through the wall face. Single-wythe applications have no continuous cavity in which to place flashing, high-performance insulation, or vapor retarders. Therefore, issues of thermal performance and moisture resistance take on added importance. WATER-REPELLENT COATINGS The newer silane and siloxane treatments (also silicone-based) can provide water repellency for 5 to 10 years while allowing the wall to breathe. INTEGRAL WATER REPELLENTS More recently, integral water-repellent admixtures have been used for both concrete block and mortar to provide moisture protection through the full depth of the wythe. Mortars treated with water-repellent admixtures achieve better bond and better moisture resistance than untreated mortars only if the admixture is compatible with the admixture used in the block. Always request manufacturer's test data on the system's flexural bond strength per ASTM C 1072 and water permeance per ASTM E 514. INSULATION, VAPOR RETARDERS The type, amount, and location of insulation affects the potential for condensation within the wall by changing the location of the dew point. Vapor retarders can help control moisture flow and condensation, but they should be used carefully.