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field for compatibility and similar reduced capillary actioncharacteristics.Integral water repellents make masonry materialshydrophobic, significantly decreasing their water absorptionand wicking characteristics. While these admixturescan limit the amount of water that can pass through unitsand mortar, they have little impact on moisture enteringthrough cracks and voids in the wall. In addition, whenusing an integral water repellent, any water that doespenetrate can not exit as easily. Therefore, even withthe incorporation of integral water repellents, flashingand weeps, as well as proper detailing of control jointsand quality workmanship are still essential. See WaterRepellents for Concrete Masonry Walls, TEK 19-1 (ref.3), and Characteristics of Concrete Masonry Units WithIntegral Water Repellent, TEK 19-7 (ref. 4), for morecomplete information on integral water repellents forconcrete masonry walls.Post-Applied Surface TreatmentsFor integrally colored architectural masonry, a clearsurface treatment should be post-applied whether or notintegral water repellent admixtures are used. Most postappliedcoatings and surface treatments are compatiblewith integral water repellents although this shouldbe verified with the product manufacturers beforeapplying. When using standard units for singlewythewalls, application of a clear treatment,portland cement plaster (stucco), paint, or opaqueelastomeric coating improves the water resistanceof the wall. Coatings containing elastomerics havethe advantage of being able to bridge small gapsand cracks. See Water Repellents for ConcreteMasonry Walls, TEK 19-1 (ref. 3) for more detailedinformation.Where it is necessary to retain some shear andflexural resistance capabilities, there are several options.One is to terminate the flashing within the inside faceshell of the wall, as shown in Figure 3. In reinforcedwalls, some shear is provided through doweling actionof the reinforcement, and by design the reinforcementtakes all tension (refs. 5, 6). Proper grouting effectivelyseals around where the vertical reinforcement penetratesthe flashing. The absence of reinforcement to providedoweling in plain masonry may be more of a concern,but loads tend to be relatively low in these applications.If structural adequacy is in doubt, a short reinforcing barthrough the flashing with cells grouted directly aboveand below can be provided as shown in Figure 3c.A better option to maintain shear at the level of theflashing is to use a product that maintains some bond inboth face shells, such as that shown in Figure 4.Ensuring that a buildup of mortar droppings doesnot clog the cells or weep holes is critical. Traditionally,a cavity filter consisting of washed pea stone or filterpaper immediately above the flashing was provided tofacilitate drainage, as shown in Figure 3. This should beaccompanied by a means of intercepting or dispersingmortar droppings, as an accumulation can be sufficientWall DrainageIn areas with high seismic loads, masonrywalls tend to be heavily reinforced and it is oftenmore economical to fully grout the masonry. Infully grouted masonry, flashing is not necessary.In these cases, the wall is designed as a barrierwall, rather than as a drainage wall.When flashing is used, the importance of properdetailing cannot be over-emphasized. Traditionally,through-wall flashing has been used to direct wateraway from the inside wall face and toward weepholes for drainage. Figure 2 shows one exampleof flashing that spans completely across the widthof the wall. In this example, the termination angleprevents any water that collects on the flashing frompenetrating to the interior, and the weeps and dripedge drain water to the exterior.Metal drip edgeAdvantages:• no need to field-cut unitsFlashingDisadvantages:• bond beam is required under flashing• bond break at flashing• exposure of flashing termination angle on insideInterior flashingtermination angleFigure 2—Three-Piece Through-Wall FlashingNCMA TEK 19-2B 3