Copyright Goodheart-Willcox Co., Inc. Chapter 12 Laying Brick 243 Workmanship In order to obtain good masonry performance, all mortar joints that are intended to receive mortar must be completely filled as the units are laid. Leaky walls result from partially filled mortar joints that can con- tribute to spalling (the deterioration or flaking off of the brick). Spalling is due to freezing and thawing when excessive moisture is present. Voids in the mor- tar can be the first location where moisture starts to enter the masonry wall surface. Keeping the Cavity Clean The cavity must be kept clean of mortar droppings and other foreign materials during the construction process. If mortar falls into the cavity, it may form bridges that stop moisture from draining or blocking the weep holes. One method of keeping the cavity clean is to place a wood or metal strip, slightly narrower than the cavity width, in the cavity or air space. The strip rests on the wall ties as the wall is built. It is pulled out prior to the place- ment of the next row of ties. In this way, any mortar that has fallen into the cavity can be removed. See Figure 12-55. A considerable amount of mortar can be eliminated from the cavity if these steps are followed: ■ ■ After spreading the mortar bed, bevel the cavity edge with the flat side of the trowel. As a result, very little mortar is squeezed out of the bed joints into the cavity when the units are laid. ■ ■ Roll the units into place, keeping most of the mortar on the outside. ■ ■ After the unit is placed on the bed joint, remove any protruding mortar fins. A mortar fin is excess mortar that protrudes from the joint on the inside of the wall cavity. The excess mor- tar should be flattened over the backs of the unit rather than cut off. This process of flattening the mortar against the back side of the masonry units is referred to as plaster back. This procedure prevents mortar from falling into the cavity and forms a smooth surface that does not interfere with the insulation. Weep Holes Weep holes allow moisture to flow from inside the wall cavity to the exterior. Weep holes can be created by Trade Tip Quality joint finishing sets apart a craftsperson from an average mason. Because of the longevity of masonry, the future work requested by customers depends on the quality and appearance of your current work! leaving out one of the head joints during construction. See Figure 12-56. Weep holes should be placed at the base of the cav- ity and at all other flashing levels to rid the structure of Beveled bed joints Wire Strip to catch mortar drippings Brick Industry Association Figure 12-55. Procedures designed to keep the cavity clean in cavity wall construction. Barbara Kalbfleisch/Shutterstock.com Figure 12-56. Shows brick over a door opening. The open weep holes are in the header course directly above doorway. The brick are supported by a metal lintel. A limestone keyway is positioned in the center of the opening.