Masonry Magazine February 1996 Page. 45
Fig. 5.
(a) The mason checks corners for alignment,
(b) for being level,
(c) and for being plumb.
The mortar should be beveled on the end of the brick to be placed so that when the brick is pressed into place, the mortar will ooze out at the top and around the sides of the head joint, indicating the joint is completely filled (Fig. 4). Dabs of mortar spotted on both corners of the brick do not completely fill the head joints, and "slushing" (attempting to fill the joints from above after the brick is placed) cannot be relied on to adequately fill head joints.
As each unit is laid, excess mortar extruding from the joints is cut off with the trowel and applied to the head joints of the unit just laid or returned to the mortarboard for reuse. If there has been any delay long enough for the extruded mortar to stiffen before it is cut off, it should be reworked on the mortarboard before reuse. Mortar droppings picked up from the scaffold or from the floor should not be reused. Mortar should not be spread too far ahead of the actual laying of units or it will tend to stiffen and lose its plasticity, thereby resulting in poor bond. In hot, dry weather it may be necessary to spread only enough mortar for a few units before they are laid.
Laying up a wall. On jobs where more than one mason is working, the foundation, footing, or shelf angles supporting the masonry must be level so that each mason can start his section of wall on a common plane and the bed joints will be uniformly straight when the sections are connected. If the support for the masonry is significantly out of level, the entire first course should be laid-establishing a level plane for subsequent courses. A line may be used to help align the units correctly. Before the corners are established, masons often lay out the masonry units for the first course without mortar to check the wall layout. The corner unit should be laid first and carefully positioned. After three or four units have been laid, the mason's level is used as a straightedge to assure correct alignment of the units. These units are then carefully checked with the level, brought to proper grade, and made plumb. It is especially important that units in the first course are properly aligned, leveled, and plumbed, since this course sets the pattern for succeeding courses.
Corner construction normally precedes laying of units between the corners. As each course is laid at a corner, it is checked with a level for alignment, for being level, and for being plumb (Fig. 5). A story pole may be used to check vertical spacing of courses.
After the corners at each end of a wall have been laid up, a mason's line (string line) is stretched tightly from corner to corner for each course, and the top outside edge of each unit is laid to this line. Different devices (line pins, line twigs, corner blocks, and line stretchers) can be used to fasten the line and eliminate sag. Careful application of these techniques will ensure true, straight walls.
Keeping cavities clean.
A drainage wall will not fulfill its intended purpose if construction practices permit mortar droppings in the drainage air-space (drainage cavity). The presence of mortar droppings on the flashing prevents exodus of water. Mortar extruded from bed joints will easily bridge cavities of one inch or less. Mortar bridges across the drainage cavity conduct water to the interior, resulting in deterioration of interior finishes. One solution is to assure that mortar spread as a bed joint is beveled or sloped away from the drainage cavity (Fig. 6). This practice requires very little effort and is a very effective means of keeping mortar out of the drainage cavity. For cavity walls having a minimum two-inch air-space between wythes, another solution is to catch mortar droppings on a board laid across a tier of ties. When masonry reaches the next level for ties, the board is raised, cleaned, and repositioned.