Building components · Frame Members
Fire Protection Casing
Explains the casing as a position around a member whose defining property is continuity, without stating any period, rating or specification of protection.
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 fire casing is
Structural members do not necessarily carry their own protection. Where protection is called for, what is added is an unbroken enclosure following the surface of the member, and it is that continuity rather than the substance forming it that the position consists of: the same continuous enclosure is reached by a sprayed coating on the member, by a film applied to it that reacts when heated, or by boards fixed around it and jointed at the corners. The material differs in each case; the position does not. It is the surface of the member, enclosed.
What makes the position worth naming separately from the materials that form it is that it is defined by continuity. A casing is only continuous where everything meeting the member has been dealt with — connections, hangers, service penetrations, ceilings and partitions arriving at it — and those junctions are where casings are commonly interrupted, first during construction and again during every later alteration. Whether protection is called for, and what any arrangement is required to do, is determined by design and by regulation and has to be verified against local requirements.
Boundaries
How it differs from nearby elements
The distinctions that keep this entry from being a restatement of its neighbours.
- It is not intumescent coating, and it is not the boards used to form it. Those are published material entries, procured and applied; the casing is the position the applied material occupies around the member, and the same position can be filled by boards, by a spray or by a coating.
- It is not a cavity barrier. A cavity barrier interrupts a void so that it is subdivided; a casing follows the surface of a member and encloses it, which is the opposite geometry and a different purpose.
- It is not a protection layer. A protection layer is placed over something vulnerable so that later work and loading do not damage it, and contributes nothing to the performance of what it covers; a fire protection casing is placed around a member precisely to act on how that member behaves, and concealment is not what either of them is for.
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.
- fire casing
- structural encasement
- boxed protection
Dependencies
What it depends on
What has to be right elsewhere for this element to do its job.
- What the design and the applicable regulations require of it, which is project-specific and has to be verified rather than assumed from the appearance of the casing.
- Continuity where other elements meet the member, since connections, hangers and abutting construction are where a casing is interrupted.
- Service penetrations through and alongside it, which are commonly formed after the casing is complete and by a different trade.
- Whether it is disturbed by later work, since protection is routinely opened up for access and reinstatement is a separate decision from removal.
Considerations
Topics that genuinely apply here
Subjects worth discussing about this element. These are discussion topics, never measured values, ratings or performance claims.
What a casing is required to do, and what a given arrangement achieves, are determined by design and by regulation, and are verified against local requirements rather than read from the casing.
Casings are formed early and met repeatedly by later trades, so the sequence between forming them and completing the work around them is where continuity is most often lost.
Protection is commonly opened up to reach connections, services or fixings above a ceiling, and whether it was reinstated as it was formed is a question that arises long after the works are finished.
What protection was specified, what was installed, and what was done at junctions and penetrations is recorded information rather than something recoverable by looking at a completed casing.
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 member hidden above a ceiling is protected. Concealment is not protection, and whether a ceiling forms part of a protection scheme depends on what the design says it is.
- That a disturbed casing can be made good with any similar-looking material. What was specified, and how it was formed at joints, junctions and penetrations, is what the arrangement depends on.
Conversations
Questions for qualified professionals
Questions worth asking someone with the project in front of them. This page cannot answer them.
- What protection does the design require for this member, and on what basis?
- How is the casing formed where connections, hangers and abutting construction meet the member?
- What was installed, and what record exists of it?
- If the casing has been opened up for access, who is responsible for reinstating it and to what?
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 states no period, rating, classification, thickness, specification or capacity of protection, and none can be inferred from it.
- Whether protection is required, what form it takes and whether any given arrangement is acceptable are matters for qualified design and for the applicable regulations, verified against local requirements for the building in question.
Structural Frame Members
The columns, beams, joists, rafters, plates and bracing that make up a load-carrying frame, identified by the position each occupies.
Browse all frame members entries →