Building components · Wall Leaves & Backing
Masonry Plinth
Explains the plinth as the zone at the foot of a wall with its own exposure conditions, distinct from the foundation below it and from bands higher up the 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 plinth is
A plinth is the base of a wall treated differently from the wall above it. The difference may be a projection, a change of unit, a change of finish, or a chamfered or moulded course marking where the base ends, and it responds to the fact that the bottom of a wall is a different environment from the rest of it.
That environment is defined by the ground. Water splashing off paving, water held against the wall by adjoining levels, frost, salts and physical impact all act at the base and at almost nowhere else. The plinth is also commonly the zone in which a horizontal damp-proof barrier sits, which makes it the part of the elevation where what is happening inside the wall becomes visible outside it.
Boundaries
How it differs from nearby elements
The distinctions that keep this entry from being a restatement of its neighbours.
- It is not a foundation. A foundation is below ground and transfers load into the ground; a plinth is the visible base of the wall above, and what it deals with is splash, frost and impact rather than bearing.
- It is not a string course. Both are horizontal bands, but a plinth is defined by being at the base of the wall where the exposure and moisture conditions differ from the rest of the elevation; a string course sits within the elevation with ordinary wall above and below it.
- It is not a damp-proof course. The damp-proof course is a published material forming a barrier within the wall; the plinth is the zone that barrier commonly sits in, and the two are frequently confused because the plinth is where the barrier is visible.
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.
- plinth course
- plinth band
- wall base
Dependencies
What it depends on
What has to be right elsewhere for this element to do its job.
- The level of the ground, paving or planting against it, since raising the external level changes what the base of the wall is exposed to.
- Where the horizontal damp-proof barrier sits relative to the external level, because the relationship between them is what determines whether the barrier can do anything.
- Drainage at the foot of the wall, since water standing against a plinth acts on it continuously rather than occasionally.
- The units used, because a denser unit at the base responds to frost and saturation differently from the wall above.
Considerations
Topics that genuinely apply here
Subjects worth discussing about this element. These are discussion topics, never measured values, ratings or performance claims.
The base of a wall is where rising moisture, splash and ground water all act, and distinguishing between them is the first step in understanding dampness at a plinth.
Rain bouncing off a hard surface at the foot of a wall wets the base repeatedly and to a height governed by the surface and the exposure, not by the wall.
Frost damage and salt crystallisation concentrate at the base of walls because that is where the masonry stays wettest for longest.
External levels around a building change over time as paving, planting and surfacing are added, and the plinth is where the consequences appear.
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 plinth is a decorative base detail. It is the part of the wall exposed to splash, ground moisture and frost, and the treatment of it is commonly a response to those conditions.
- That dampness at a plinth means the barrier within the wall has failed. Raised external levels, blocked drainage and splash from paving produce similar symptoms without anything inside the wall having changed.
Conversations
Questions for qualified professionals
Questions worth asking someone with the project in front of them. This page cannot answer them.
- Where does the horizontal damp-proof barrier sit relative to the external ground level along this wall?
- Has the external level been raised at any point since the wall was built?
- Is dampness at this base rising, splashing, penetrating or a combination, and what evidence separates them?
- How does water drain away at the foot of this wall?
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 zone of a wall. It states no height, no projection, no level relationship and no moisture performance, and none can be inferred from it.
- Diagnosing dampness at the base of a wall requires investigation on site; nothing here identifies a cause or a remedy for any particular building.
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 →