Made of brick, clay tile, architectural concrete masonry, or special concrete screen block, masonry screen walls can provide shade, block wind, hide unsightly objects or property, and provide privacy from adjacent city streets, alleys, or neighbors. BRICK AND CLAY TILE WALLS Standard height-to-thickness ratios for conventional exterior solid brick walls limit the span or height of 4-inch walls to 6 feet and 8-inch walls to 12 feet. Brick and tile screen walls should be built more conservatively. The open head joints and intermittent bed joints reduce the wall's flexural stability against wind loads and prohibit the use of joint reinforcement. CONCRETE MASONRY WALLS In contrast to brick screen walls, most concrete masonry screens are built with continuous horizontal mortar joints. In fact, both head and bed joints are fully mortared. This larger area of mortar bonding increases the lateral load resistance of the wall. Type S mortar and truss-type joint reinforcement are recommended. Because of their decorative holes, the way screen block are positioned in the wall greatly affects their load-carrying capacity. KEEPING WATER OUT How do you keep water out of a screen wall that is full of decorative holes? You can't completely. Water is going to get into the wall, but there is no place for it to be trapped inside. The openings that allow the water to get in also allow it to rapidly drain and evaporate.