bond

A bond is the deliberate overlapping pattern in which bricks or masonry units are laid to create a unified, structurally sound wall. Each brick is offset from the ones directly above and below it, so that vertical joints never align continuously through the thickness of the wall. This staggering distributes load across multiple units and prevents the mortar joints from forming a continuous weak plane that could cause the wall to split or fail.

The most common bonds in modern construction are stretcher bond (also called running bond), where all visible faces show long sides of the brick; and English bond, which alternates rows of stretchers with rows of headers (short ends facing out). English bond uses more headers, which lock the front and back of a wall together and was standard in load-bearing masonry for centuries. Flemish bond interweaves headers and stretchers within each row and is favored for its appearance on visible walls. Stack bond, where bricks align vertically, offers a clean look but is weaker and typically requires additional reinforcement.

Strength through overlap

The bond pattern determines how effectively a wall resists cracking and collapse. When bricks are bonded properly, a crack in one unit does not propagate straight up the wall because the next course has bricks running in a different direction. The overlap ensures that forces are transferred laterally through the masonry and distributed to surrounding units. Poor bonding, or relying on mortar alone to hold units in place, leaves walls vulnerable to bowing, bulging, and separation along vertical planes.

In cavity walls and veneer construction, the bond must also account for ties or connectors that transfer loads between the outer facing and the inner structural layer. The header courses or tie positions must align correctly to maintain this connection. Modern codes specify minimum tie spacing and material to ensure the veneer does not separate from the backing.

The term comes from the binding or pledging together of units; historically, masons spoke of bricks being bonded into a cohesive structure. The pattern itself was not invented but developed empirically across centuries of brick building, with regional and trade-specific variations. Today, bond pattern selection depends on whether the wall is load-bearing, the aesthetic requirement, material availability, and local building code approval.