Masonry Magazine February 1996 Page. 46
Fig. 6. Beveling the inside bed joint helps keep mortar out of a wall cavity.
Installing flashing and weepholes. Flashings are used to control water that may penetrate the outer wythe of masonry by providing direct drainage through weepholes to the exterior of the building. To function properly, it is important that the flashing extend to the outer face of the masonry, preferably slightly beyond the face forming a drip. Care must be taken to avoid tearing or puncturing flashing during installation. All seams must be lapped at least 6 in. (150 mm) and sealed. The inside upper edge of the flashing must be installed so that water does not get behind the flashing. End dams must be installed wherever flashings terminate (Fig. 7).
Ties and anchors. Wall ties are used to connect two masonry wythes together so that they act together to resist applied loads. Ties are also used to connect a masonry veneer to a structural back-up wall. Anchors are used to connect masonry walls to intersecting walls or other structural members. A variety of ties and anchors are used in masonry construction. The selection depends on the requirements of the specific application and is part of the design process. The project drawings and specifications should identify the type, size, and location of these connectors.
Proper installation of connectors is critical to the performance of the masonry. Wall ties should be installed such that the embedded end extends at least 1/2 in. (12 mm) into the outer face shell bedding of masonry constructed using hollow units and at least 1 1/2 in. (38 mm) into the mortar bed of masonry constructed using solid units. Bending wall ties from the manufactured shape changes their ability to transfer loads. Many building codes prohibit bending of ties unless approved by the architect or engineer.
Anchors are often designed to transfer loads in one direction but allow movement in another. For example, joint stabilizing anchors resist lateral loads but allow shrinkage and expansion through the connector (Fig. 8). The mason should understand the purpose of these accessories and properly install them so they can function as designed.
Fig. 7. End dams must be formed wherever flashings terminate in a wall.
Weepholes are located over the flashing at the bottom of drainage walls. They can be formed by leaving an open head joint, or by installing a weephole vent or cotton sashcord in a mortared head joint. The weephole must provide an unobstructed pathway to the exterior for the drainage of water collected by the flashing.
Fig. 8. Joint stabilizing anchors connect intersecting walls and allows shrinkage or expansion through the joint.
Movement joints. Clay masonry units expand slightly as they are exposed to moisture. Concrete masonry units shrink as they cure and dry. Movement joints are used to accommodate dimensional changes in masonry elements resulting from moisture and temperature changes. Determination of the required type and location of movement joints is part of the design process, and that information should be contained in the project drawings and details.
46 MASONRY-JANUARY/FEBRUARY, 1996