can vary the common bond with a Flemish header course. In laying out any bond pattern, be sure to start the corners correctly. In a common bond, use a three- quarter closure at the corner of each header course.

In the Flemish bond, each course consists of alternating headers and stretchers. The headers in every other course center over and under the stretchers in the courses in between. The joints between stretchers in all stretcher courses align vertically. When headers are not required for structural bonding, you can use bricks, called blind headers. You can start the corners in two different ways. In the Dutch corner, a three-quarter closure starts each course. In the English corner, a 2-inch or quarter closure starts the course.

The English bond consists of alternating courses of headers and stretchers. The headers center over and under the stretchers. However, the joints between stretchers in all stretcher courses do not align vertically. You can use blind headers in courses that are not structural bonding courses.

The stack bond is purely a pattern bond without overlapping units; however, all vertical joints are aligned. You must use dimensionally accurate or carefully rematched units to achieve good vertical joint alignment. You can vary the pattern with combinations and modifications of the basic patterns shown in figure 4-4. This pattern usually bonds to the backing with rigid steel ties or 8-inch-thick stretcher units when available. In large walled areas or load-bearing construction, insert steel pencil rods into the horizontal mortar joints as reinforcement.

The English cross, or Dutch, bond is a variation of the English bond. It differs only in that the joints between the stretchers in the stretcher courses align vertically. These joints center on the headers in the courses above and below.

When a wall bond has no header courses, use metal ties to bond the exterior wall brick to the backing courses. Figure 4-5 shows three typical metal ties.

Install flashing at any spot where moisture is likely to enter a brick masonry structure. Flashing diverts the moisture back outside. Always install flashing under horizontal masonry surfaces, such as sills and copings; at intersections between masonry walls and horizontal surfaces, such as a roof and parapet or a roof and chimney; above openings (doors and windows, for example); and frequently at floor lines, depending on the type of construction. The flashing should extend through the exterior wall face and then turn downward against the wall face to form a drop.

Figure 4-5. - Metal ties.

You should provide WEEP HOLES at intervals of 18 to 24 inches to drain water to the outside that might accumulate on the flashing. Weep holes are even more important when appearance requires the flashing to stop behind the wall face instead of extending through the wall. This type of concealed flashing, when combined with tooled mortar joints, often retains water in the wall for long periods, and by concentrating the moisture at one spot, it does more harm than good.

MORTAR JOINTS AND POINTING

No set rule governs the thickness of a brick masonry mortar joint. Irregularly shaped bricks may require mortar joints up to one-half inch thick to compensate for the irregularities. However, mortar joints one-fourth inch thick are the strongest. Use this thickness when the bricks are regular enough in shape to permit it.

A slushed joint is made simply by the deposit of mortar on top of the head joints and allowing it to run down between the bricks to form a joint. You cannot make solid joints this way. Even when you fill the space between the bricks completely, there is no way you can compact the mortar against the brick faces; consequently, a poor bond results. The only effective way to build a good joint is to trowel it.

The secret of mortar joint construction and pointing is in how you hold the trowel for spreading mortar. Figure 4-6 shows the correct way to hold a trowel. Hold it firmly in the grip, as shown, with your thumb resting on top of the handle, not encircling it. If you are right-handed, pick up the mortar from the outside of the mortar board pile with the left edge of your trowel (fig. 4-7, view 1). You can pick up enough to spread one to five bricks, depending on the wall