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An information series from the national authority on concrete masonry technologyDESIGN FOR DRY SINGLE-WYTHECONCRETE MASONRY WALLS TEK 19-2BWater Penetration Resistance (2012)INTRODUCTIONSingle-wythe concrete masonry walls are cost competitivebecause they provide structural form as well asan attractive and durable architectural facade. However,because they do not have a continuous drainage cavity(as do cavity and veneered walls), they require specialattention to moisture penetration.The major objective in designing dry concrete masonrywalls is to keep water from entering or penetratingthe wall. In addition to precipitation, moisture can findits way into masonry walls from a number of differentsources (see Figure 1). Dry concrete masonry walls areobtained when the design and construction addressesthe movement of water into, through, and out of thewall. This includes detailing and protecting buildingelements including parapets, roofs, all wall penetrations(utility and fire protective openings, fenestration, doors,etc.), movement joints, sills and other features to resistwater penetration at these locations. Annotated Designand Construction Details for Concrete Masonry (ref. 1)contains comprehensive details for reinforced and unreinforcedconcrete masonry walls. Further, condensationand air leakage must be controlled. See the CondensationControl section on page 7.The primary components of moisture mitigation inconcrete masonry walls are flashing and counter flashing,weeps, vents, water repellent admixtures, sealants (includingmovement joints), post-applied surface treatments,vapor retarders and appropriate crack control measures.For successful mitigation, all of these components shouldbe considered to be used redundantly, however not allwill be applicable to all wall systems. For example,flashing and weeps are not necessary in solidly groutedconstruction, and may not be appropriate in areas of highRelated TEK:5-15, 6-2B, 6-11A, 6-14A, 6-17B, 8-4A, 9-1A, 10-1A, 10-2C, 19-1, 19-3A, 19-4A, 19-5A, 19-6, 19-7wind or seismic loading where compromise of masonryshear resistance may occur (see the Wall Drainage sectionon page 3 for more information). The determinationon structural effect must be made by the structuralengineer. As another example, the use of integral waterrepellents for surfaces to receive a stucco finish may notbe appropriate. Successful design for moisture mitigationconsiders each of these components, and providesSolarheatVapor flow73°F (23°C) 10% R.H.*73°F (23°C) 75% R.H.*85°F (23°C) 50% R.H.*GradeGround waterpenetrationRain* Relative humidityFlashingAbsorptionpenetrationMoist high R.H.* air(condenses on cooling)Vapor rises astemperature increasesFigure 1—Moisture Sources73°F (23°C) 50% R.H.*73°F (23°C) 50% R.H.*85°F (23°C) 50% R.H.*Keywords: architectural, capillary action, coatings,construction details, design for redundancy, flashing,moisture, single-wythe, tooling mortar joints, walldrainage, water resistance, water repellents, weepsNCMA TEK 19-2B 1