inbond
Of a brick or stone: laid with its length across the thickness of a wall.
inbond: a brick laid sideways into the wall's depth
An inbond brick is one oriented so that its length runs perpendicular to the face of the wall, pushing its short dimension across the full or partial thickness of the wall structure. This contrasts with a stretcher, where the long dimension runs parallel to the wall face. The inbond arrangement creates what is technically called a header course when the practice is systematic across an entire horizontal layer.
The primary purpose of inbond placement is structural: it ties the wall's outer and inner leaves together, preventing them from separating under load or weather pressure. In multi-leaf masonry (typically two or three brick widths thick), inbond bricks create mechanical locks between layers. On a single-leaf wall, an inbond brick improves resistance to lateral forces by distributing stress through the depth of the wall rather than just along its face.
In Flemish bond, the most common decorative bonding pattern in brickwork, inbond bricks alternate with stretchers in each course. In English bond, alternate courses are entirely inbond, creating a more heavily cross-tied structure that was standard for load-bearing walls. The frequency of inbond bricks increases as wall thickness or structural demands increase. A six-inch cavity wall might use inbond every fifth course; a nine-inch solid wall every third or fourth.
The term comes directly from the idea that the brick is bonded in to the depth of the wall. Period brickwork manuals refer to "heading" as the action of laying an inbond brick. Poor inbond placement or omission of inbond bricks leaves walls vulnerable to delamination, where layers can separate under wind load or freeze-thaw stress, particularly visible as horizontal cracks at the interface between leaves.
Modern reinforced concrete and steel-frame construction has reduced reliance on traditional bonding patterns for structural integrity, since frames carry the load. However, inbond principles remain relevant in cavity wall tie selection, where ties must achieve the same through-wall connection that systematic inbond once provided. Heritage masonry repair and conservation work demands understanding of original bond patterns to maintain structural coherence.