Building components · Wall Leaves & Backing
Quoin
Explains the quoin as the position where two wall faces become one corner, which is a structural junction as well as the most visible part of an elevation.
Educational reference entry. What this element has to do, and whether any particular arrangement of it is adequate, depends on the whole assembly, the loading, the exposure, local requirements, the manufacturer's instructions and qualified professional design.
Overview
What a quoin is
A quoin is the corner of a masonry wall: the units at the external angle where two faces meet. In bonded construction the units at that angle alternate their direction course by course, so that each face reaches into the other and the corner is built as one element rather than as two walls arriving at the same point.
Quoins are commonly emphasised — in a different material, a larger unit or a projecting face — and that emphasis is easy to read as purely decorative. In much traditional construction it reflects the fact that the corner is doing more work and taking more exposure than the wall between corners.
Boundaries
How it differs from nearby elements
The distinctions that keep this entry from being a restatement of its neighbours.
- It is not a masonry pier. A pier is a thickening of the wall that stiffens it or receives a concentrated load; a quoin is at the angle between two faces, its job includes tying those faces together, and it involves no change in the wall's thickness.
- It is not a corner trim or bead. Trims and beads are applied over a corner once the wall is built; a quoin is built into the wall as it rises and is part of the masonry itself.
- It is not only decoration, even where quoins are formed in a contrasting material for appearance alone — in bonded masonry the same position is also what makes the two returning faces act as one corner.
Terminology
Common names and aliases
These names describe the same element. The library keeps one entry per component so that a trade term or a regional name never becomes a second, thinner page.
- corner stones
- angle stones
- quoin stones
Dependencies
What it depends on
What has to be right elsewhere for this element to do its job.
- Whether the two faces are genuinely bonded at the angle or merely built up against one another, which governs whether the corner acts as one element.
- The coursing of both faces arriving at the same levels, since a corner is where any discrepancy between them becomes unavoidable.
- The exposure at the corner, which is commonly more severe than along the wall because wind and rain act on two faces at once.
- Whether the quoin units differ from the wall units in absorption, strength or movement behaviour, since a change of material at the corner is also a change of behaviour there.
Considerations
Topics that genuinely apply here
Subjects worth discussing about this element. These are discussion topics, never measured values, ratings or performance claims.
A corner is exposed on two faces and to wind moving around it, which is why decay and saturation frequently appear at quoins before they appear elsewhere on an elevation.
The corner is where the setting out of two walls has to reconcile, so coursing errors that were invisible along a face become visible here.
Where quoin units are of a different material from the wall, the two move differently, and the junction between them is where that difference shows.
A bonded corner lets each face restrain the other, which is part of how a masonry wall resists being pushed over.
Materials
Commonly formed from
Material families this element is commonly realised in. This states common practice only — it is not a statement that any of these materials suits this component in a particular building, which depends on the whole assembly and on qualified review.
Assemblies
Building systems this element is met in
The role this component fills inside each assembly. A role describes what the element does there — it is not a statement that this component suits that system in any particular building.
Clarifications
Commonly misunderstood
- That a corner can be rebuilt in the same material and be the same corner. What makes a quoin work in bonded masonry is that each face reaches into the other, and that is a question about the bonding rather than about the units used.
- That a corner can be rebuilt as two separate faces. Unless the courses of each face reach into the other, the corner is two walls meeting rather than one corner.
Conversations
Questions for qualified professionals
Questions worth asking someone with the project in front of them. This page cannot answer them.
- Are the two faces at this corner bonded together, or built against one another?
- Are the quoin units a different material from the wall, and how do the two behave relative to each other?
- Is deterioration at this corner related to exposure, to the bonding, or to something arriving at the corner from above?
- How is the coursing of both elevations being reconciled at this angle?
Go deeper
Related Build Design Hub guides
Planning guidance behind the decisions this element involves.
Preparation
Related planning checklists
Owner-side preparation before the conversation where this element comes up.
What this entry does not do
- This entry describes a position in a wall. It states no unit size, no bonding specification, no projection and no structural capacity, and none can be inferred from it.
- Whether a particular corner is adequately bonded, or why it has deteriorated, is a matter for inspection and structural assessment rather than a reference entry.
Wall Leaves & Backing
The distinct vertical layers that make up a wall — outer and inner leaves, the cavity between them, and the backing that supports what is fixed to the face.
Browse all wall leaves & backing entries →