Building components · Wall Leaves & Backing
Corbel
Explains the corbel as support built out of the wall's own courses, distinct from a bracket fixed to a wall and from a bearing introduced between two elements.
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 corbel is
A corbel is masonry that projects from a wall face because each course steps out beyond the one beneath it. The projection can be a single course or a series of them, and it produces a ledge, a seating or a widening where the plain wall would offer nothing.
What holds a corbel in place is the weight of the masonry above it. Each projecting course is held down at its back by what sits on it, and the projection is limited by that balance rather than by the strength of the units. This is why the wall above a corbel matters as much as the corbel itself, and why a corbel cannot be understood in isolation from the masonry it belongs to.
Boundaries
How it differs from nearby elements
The distinctions that keep this entry from being a restatement of its neighbours.
- It is not a structural bearing. A bearing is a discrete component introduced between two elements to control how load passes between them; a corbel is masonry of the wall itself, projecting to create a seating where none existed.
- It is not a bracket. A bracket is a separate component fixed to a wall face; a corbel is built out of the wall's own courses as the wall rises, and it cannot be added to a completed wall in the same way.
- It is not a cantilever in the beam sense. A cantilever resists bending along its length; a corbel works by each course oversailing the one below while the weight of the masonry above holds its tail down, so removing that weight changes the whole arrangement.
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.
- corbelling
- corbel course
- stepped projection
Dependencies
What it depends on
What has to be right elsewhere for this element to do its job.
- The masonry above it, since the projection is held down by what bears on the back of each projecting course.
- The bonding of the courses, because the projection relies on the wall behaving as one element rather than as separate units.
- What lands on it, since a corbel formed as a feature and a corbel carrying a member are the same position doing very different work.
- The wall's own stability, as a projection applies its load off the centre of the wall rather than through it.
Considerations
Topics that genuinely apply here
Subjects worth discussing about this element. These are discussion topics, never measured values, ratings or performance claims.
Load applied at a projection acts away from the centre of the wall, so a corbel changes how load travels down the wall as well as where it starts.
Corbelling is built as the wall rises and depends on the courses above being in place, which is why it is not something that can convincingly be introduced afterwards.
A projecting course interrupts water running down the face and presents an upper surface where water and debris can sit.
The joints at a projection are more exposed than those in the wall face, and deterioration there affects the projection rather than only its appearance.
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.
Related elements
Neighbouring components
Typed relationships to other elements. There is deliberately no generic “related” category: an edge that cannot be classified does not exist.
Clarifications
Commonly misunderstood
- That corbels are decorative brackets. Where they carry something, the projection is the support, and what is above it is what makes the support possible.
- That the masonry above a corbel can be altered independently. Removing or opening up the wall above changes what holds the projecting courses down.
Conversations
Questions for qualified professionals
Questions worth asking someone with the project in front of them. This page cannot answer them.
- Is this corbel carrying anything, and if so what lands on it?
- What masonry above the projection is holding it down, and is any of it proposed to change?
- Are the projecting courses bonded into the wall or built as a face feature over it?
- Is movement or cracking near this projection related to the load it carries or to the wall around it?
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 form of construction. It states no projection, no number of courses, no bearing area and no load capacity, and none can be inferred from it.
- Whether a particular corbel can carry a proposed load, or can remain if the wall above is altered, is a structural question for a qualified professional on site.
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 →