Masonry bond patterns are specific arrangements of bricks or other masonry units within a structure. These patterns are fundamental to brickwork, serving both practical and visual purposes. The careful placement of each unit ensures the wall functions as a cohesive system, defining durable and well-built masonry.
Understanding Masonry Bond Patterns
Stretcher Bond, also known as Running Bond, features bricks laid with their long, narrow faces visible. Each brick in a course overlaps the one below by half its length, creating a clean, horizontal line. This pattern is frequently used for half-brick thick walls, such as partition walls or the outer layer of cavity walls, due to its simplicity.
Header Bond features bricks laid with their short, square ends, or “headers,” facing outward. This creates a textured appearance with exposed brick ends. Header bonds are used for full-brick thick walls, curved walls, or as decorative elements, forming strong, thick walls.
English Bond is a strong traditional bond, alternating entire courses of stretchers with entire courses of headers. In this pattern, headers in a header course are centered over the stretchers below. This arrangement is widely applied in load-bearing walls, foundations, and bridges where high structural integrity is important.
Flemish Bond presents a more decorative appearance while providing good strength. Headers and stretchers are alternated within the same course. Headers in one course are typically centered over the stretchers below, creating a distinctive checkerboard-like effect. This bond is often selected for facades or high-quality brickwork where both strength and aesthetics are desired.
Common Bond, sometimes called Garden Wall Bond, is similar to Stretcher Bond but includes intermittent courses of header bricks. These header courses add structural stability, making it suitable for non-load-bearing walls like garden walls. Stack Bond, by contrast, involves stacking all bricks directly on top of each other, with no overlapping joints. This bond is primarily decorative, lacking significant structural stability, and is often seen in modern designs.
How Bond Patterns Influence Structural Integrity
The interlocking nature of masonry bond patterns is fundamental to distributing loads and enhancing a wall’s stability. When bricks are laid with staggered joints, they are woven together, which increases the overall strength of the construction. This interlocking prevents individual bricks from shifting and helps the wall act as a unified structure under various forces.
Different bond patterns have varying capacities for load distribution. In running bond construction, which features staggered vertical joints, compressive strength is comparable to stack bond construction. However, in stack bond masonry, where vertical joints are continuous, concentrated loads are carried primarily by the vertical column of masonry directly beneath the load, with limited distribution to adjacent areas. To compensate, reinforced bond beams or grouted cells can improve load distribution and resistance to concentrated forces in stack bond walls.
The flexural strength, or resistance to bending, of a wall is also influenced by the bond pattern. Unreinforced masonry walls laid in running bond exhibit greater flexural resistance when spanning horizontally compared to walls with other patterns. Building codes may require horizontal reinforcement in walls not laid in running bond to achieve comparable flexural strength. This reinforcement helps to distribute stresses and prevent cracking from thermal movement or structural deficiencies.
The in-plane shear strength of an unreinforced masonry wall is heavily dependent on the bond pattern and the type of masonry units used. Running bond patterns can provide a substantial increase in shear capacity, potentially nearly four times the strength of masonry not laid in running bond and not constructed with open-ended units. For walls not laid in running bond, using open-ended units that allow grout to fill the void space and interlock the cells can increase shear strength by at least two times.
The Aesthetic Role of Bond Patterns in Design
Masonry bond patterns contribute significantly to a building’s visual appeal, creating distinct textures and shadow lines. The arrangement of bricks, whether exposing their long “stretcher” faces or short “header” faces, directly impacts the pattern and overall design aesthetic. This choice of bond can evoke different architectural styles, from traditional to contemporary, influencing the perceived scale and visual interest of a structure.
The way sunlight interacts with the brickwork is affected by the bond pattern, as different patterns create varied shadow depths and lines. For example, a stack bond, with its continuous vertical and horizontal joints, emphasizes verticality and can achieve a modern aesthetic, especially when paired with specific brick colors like white or black. Contrasting brick colors within a header bond can also produce decorative effects.
Mortar joints play a substantial role in enhancing or altering the visual impact of a chosen bond pattern. The color of the mortar can either blend with the bricks, creating a more uniform appearance, or contrast sharply to produce a compelling and eye-catching design. A darker mortar can make the overall wall appear darker and the bricks richer in color, while a lighter mortar can make the bricks seem lighter.
Beyond color, the profile of the mortar joint adds to the wall’s texture and visual depth. Joint profiles like concave or V-shaped joints can create sharper shadow lines and improve water resistance by compacting the mortar. The total area of mortar, which can account for 17% to 25% of the wall’s surface depending on the bond pattern, also influences the overall perceived color and texture of the masonry.