Masonry construction consists of individual units (bricks, blocks, or stone) held together with mortar. Masonry provides durability, fire resistance, and aesthetic appeal. Common masonry units include clay bricks (typical size 7.6 x 3.6 x 2.4 inches), concrete blocks (typically 7.6 x 7.6 x 15.6 inches), and natural stone. Mortar is a mixture of Portland cement, lime, sand, and water that bonds units together. Mortar strength and flexibility must be appropriate to the unit type and application. Standard mortar types include Type N (general purpose), Type S (higher strength), and Type M (maximum strength). Bond patterns (arrangement of units) affect strength and appearance. Running bond (offset rows) is most common. Stack bond (aligned rows) is simpler but less strong. Other patterns including Flemish bond, English bond, and herringbone bond are used for aesthetic purposes. Masonry veneer over wood frame provides aesthetic benefits of masonry with lighter construction cost. The veneer is attached to the frame with metal ties and must have proper flashing and drainage behind it. Solid masonry walls (non-veneer) must be designed and constructed to resist lateral loads from wind and seismic forces. Masonry strength depends on unit strength, mortar strength, and construction quality. Low-strength mortar in high-strength units (or vice versa) reduces overall performance. Quality control during construction is important; proper mortar joint thickness (typically 3/8 inch) and complete filling of joints ensures maximum strength. Exposed masonry may be sealed with clear or water-repellent sealers to prevent water penetration and staining. Movement joints (control joints) accommodate expansion and contraction from temperature and moisture changes. Lack of movement joints causes cracking. Maintenance of masonry includes repointing deteriorated mortar joints, which extends wall life significantly.