A quoin is an exterior corner element of a masonry or veneered wall composed of individual, often larger or more pronounced blocks or units. In construction and inspection contexts, it refers to the stones, bricks, or cast‐stone pieces that form the corners of a building, both reinforcing the edge structurally and providing an aesthetic accent that differentiates the corner from the field of the wall.
Fabricating and installing quoins requires precise layout and mortar joint planning to ensure that each unit interlocks correctly with adjacent courses, maintaining both plumb alignment and consistent joint widths. In residential applications, quoins are frequently fashioned from natural stone, precast concrete, or specialized brick to add visual interest and convey solidity on homes, townhouses, or garden walls. Commercial or institutional buildings may employ larger, load-bearing stone quoins integrated into structural masonry, where they also help resist lateral loads at corners. Quoins differ from standard corner bricks or stones in that they are typically distinct in size, material, or finish, creating a deliberate contrast with the main wall surface.
I recommend verifying that each quoin unit is fully bedded on a uniform mortar joint, that corner units are checked for plumb and level before pointing, and that the mortar color matches or complements adjacent brick or stonework to avoid unsightly discoloration over time.