Building components · Openings & Frames
Opening Reveal
Explains the reveal as the visible symptom surface for what is happening within the jamb behind it.
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 reveal is
The reveal is the surface you see when you look into an opening from the side: the return from the wall face to the frame. It is a finish, but it is a finish over the jamb, and what is behind it determines how it behaves.
It is the place where a thermal bridge around an opening becomes visible. Because the reveal is the coldest internal surface near a window, condensation and mould appear there before they appear anywhere else in the room.
Boundaries
How it differs from nearby elements
The distinctions that keep this entry from being a restatement of its neighbours.
- It is not the jamb. The jamb is the whole edge condition through the wall; the reveal is the visible surface finishing it.
- It is not a window board. The board is the horizontal surface at the sill; the reveal returns vertically at the sides and across the head.
- It is not architectural trim. Architrave and trim cover the joint between reveal and frame; the reveal is the returned surface itself.
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.
- reveals
- window reveal
- returns into the opening
Dependencies
What it depends on
What has to be right elsewhere for this element to do its job.
- The insulation behind it, since the reveal's surface temperature follows from what is in the jamb.
- How it meets the frame, which is where a joint between two different materials sits.
- Whether it is continuous with the wall finish or a separate element.
- The depth of the reveal, which follows from where the frame sits within the wall's thickness.
Considerations
Topics that genuinely apply here
Subjects worth discussing about this element. These are discussion topics, never measured values, ratings or performance claims.
Reveals are the first surfaces to show the consequences of an insulation gap around an opening, which makes them a useful diagnostic rather than merely a finish.
Mould at a reveal is commonly a surface-temperature problem in the construction rather than a ventilation problem in the room.
The joint between reveal and frame is between two materials that move differently, and it is the joint most likely to crack.
The reveal is finished last, which means it conceals whatever was or was not done in the jamb behind it.
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.
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.
Reveal to Frame
Where the internal finish returns into an opening and meets the frame, on the coldest internal surface near a window.
Raises: Thermal continuity · Moisture · Movement · Air leakage
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 mould on a reveal is a cleaning or ventilation matter. It usually indicates that the surface is colder than the rest of the room, which is a construction issue.
- That the reveal is purely decorative. It is the visible face of the jamb, and it reports on it.
Conversations
Questions for qualified professionals
Questions worth asking someone with the project in front of them. This page cannot answer them.
- What insulation is behind this reveal, and is it continuous?
- Is condensation on the reveal consistent with a thermal bridge in the jamb?
- How is the joint between reveal and frame formed, and does it accommodate movement?
- Where does the frame sit in the wall thickness, and does that position affect the reveal's temperature?
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 dimension, insulation arrangement, surface temperature or finish specification is stated here.
- Persistent condensation and mould are investigated by establishing why a surface is cold, which requires assessment of the construction.
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 →