Building components · Openings & Frames
Cavity Closer
Explains the closer as a solution to a genuine conflict — the cavity must be closed and must not be bridged.
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 cavity closer is
Where an opening is formed in a cavity wall, the cavity is cut open at the jamb, head and sometimes sill. Something has to close that edge — otherwise the cavity is open to the opening — but whatever closes it sits between the two leaves and is therefore a potential bridge.
A cavity closer resolves that: it closes the edge while being insulating enough not to be a significant thermal path, and arranged so that water on the outer leaf is not conducted to the inner one.
Boundaries
How it differs from nearby elements
The distinctions that keep this entry from being a restatement of its neighbours.
- It is not a cavity barrier. A barrier subdivides a cavity for fire reasons within the wall; a closer finishes the cavity at an opening.
- It is not insulation in the general sense. It is a component doing a specific job at an edge, even though it is insulating.
- It is not the jamb. The jamb is the position; the closer is a component within it.
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.
- cavity closers
- insulated closer
- reveal closer
Dependencies
What it depends on
What has to be right elsewhere for this element to do its job.
- Being insulating enough that closing the cavity does not create a cold path around the opening.
- Not providing a route for water to cross from the outer leaf to the inner one.
- Fitting the actual cavity, since a closer that does not fit leaves a gap on one side or the other.
- Its relationship with the frame, which is commonly fixed to or against it.
Considerations
Topics that genuinely apply here
Subjects worth discussing about this element. These are discussion topics, never measured values, ratings or performance claims.
A closer that is not insulating turns the whole perimeter of an opening into a cold path, which shows on the reveals.
The closer sits between a leaf that gets wet and a leaf that must not, so it has to close without conducting.
Cavity widths vary in practice, and a closer that does not match the actual cavity leaves gaps at exactly the position it exists to close.
In some constructions the closer also has a fire role at the opening perimeter, which is a separate requirement from the thermal one.
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.
Materials
Commonly incorporates
Materials this element commonly contains as a distinct constituent part, rather than being made of.
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.
Junctions
Interfaces this element takes part in
Junctions where the condition between this element and another governs how the construction behaves. These name the junction and the subjects it raises; they are not details, arrangements or approved ways of building.
Cavity Closer to Frame
Where the element closing the cavity meets the frame, and where the opening's thermal perimeter is either continuous or not.
Raises: Thermal continuity · Moisture · Air leakage · Fire continuity
Where it is met
Application contexts
Building contexts where this element is commonly encountered. Association is not recommendation: appearing here does not mean the component suits every instance of that context, or any particular one.
- Opening
Clarifications
Commonly misunderstood
- That returning the outer leaf into the opening closes the cavity acceptably. It bridges the leaves, which is what the cavity exists to prevent.
- That a closer is a trim. It is a thermal and moisture component at the edge of the wall's build-up.
Conversations
Questions for qualified professionals
Questions worth asking someone with the project in front of them. This page cannot answer them.
- What closes the cavity at the openings in this wall?
- Does the closure avoid bridging the leaves for moisture?
- Is the closer insulating enough to avoid a cold path around the opening?
- Does the closer suit the actual cavity width as built?
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
- No cavity width, closer type, thermal value or fire performance is stated here.
- Opening perimeter arrangements in cavity walls are subject to thermal and fire regulation and require qualified design.
Openings & Frame Elements
The frames, heads, jambs, sills, thresholds and closers that form and finish an opening through a wall.
Browse all openings & frames entries →