Glossary · Two-word term
Fire Stops
In short
materials or systems used to seal openings and prevent fire penetration
Fire stops are specialized materials or systems used to seal structural openings and junctions to prevent fire spread. Within UK cladding systems, they maintain the integrity of fire-separating elements where the external wall meets the building’s internal compartments.
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Fire Stops
Definition and Core Function
In the context of the UK built environment, fire stops are materials or systems used to seal openings and prevent fire penetration within a building's structure. While often discussed alongside general fire safety measures, their application within external wall systems is specialized. Unlike cavity barriers, which are designed to close the void between the inner leaf and the cladding panel, fire stops are typically employed to maintain the integrity of fire-separating elements where they are breached by services or structural components.
The fundamental objective of fire stopping is to restore the fire resistance of a compartment wall or floor. In cladding and external wall remediation, this involves ensuring that the junction between the internal compartmentation and the external envelope does not become a path for the transmission of heat or flame. Fire stops must be tested to demonstrate they can withstand fire for a specific duration, typically measured in minutes of integrity and, where required, insulation.
Application in External Wall Systems
Fire stops are integral to the continuity of the building fabric. In complex external wall assemblies, they are frequently located at the interface where a floor slab meets the curtain walling or cladding system. This junction is a critical point of potential failure; if left unsealed, it could allow fire to bypass the floor’s fire-resisting capabilities and travel vertically through the building’s perimeter.
During cladding repair or replacement projects, the condition of existing fire stopping is a primary concern. Technical assessments often reveal that while fire stops were specified in original designs, they may have been incorrectly installed, damaged during subsequent works, or may have degraded over time. When a cladding system is removed, it provides a unique opportunity to inspect these concealed elements and ensure that the seals between the building's structural frame and the external facade are robust and continuous.
Regulatory Context in England and Wales
The installation and maintenance of fire stops are governed by the Building Regulations, specifically Requirement B3 of Schedule 1, which mandates that the building shall be designed and constructed so that, in the event of fire, its stability will be maintained for a reasonable period. Approved Document B (Fire Safety) provides guidance on how to meet these requirements, outlining the necessity for fire stopping in all openings around penetrating services and at junctions between fire-separating elements.
For higher-risk buildings, the regulatory framework has become more stringent following the introduction of the Building Safety Act 2022. The emphasis is now placed on the "Golden Thread" of information, requiring detailed records of what products were used and how they were installed. In the context of cladding, this means that any fire stopping work undertaken during remediation must be meticulously documented, often involving photographic evidence and sign-off by a competent professional to satisfy the Building Safety Regulator.
Considerations for Building Owners and Managers
Building owners, Managing Agents, and directors of Resident Management Companies (RMC) or Right to Manage (RTM) companies must view fire stops as a critical component of the building’s passive fire protection strategy. Unlike active systems like sprinklers, fire stops are passive; they do not require mechanical activation, but their effectiveness is entirely dependent on correct installation and the absence of subsequent disturbance.
During an EWS1 assessment or a PAS 9980 appraisal, the adequacy of fire stopping is often a focal point. If the assessment identifies deficiencies, it may necessitate intrusive investigations or remedial works. It is important for stakeholders to understand that fire stops are not a "one size fits all" product. The choice of material—whether intumescent sealants, fire-rated mortars, or mineral fibre batts—must be compatible with the surrounding substrates and the specific fire resistance requirements of that section of the building.
Fire Stops
Common Misunderstandings
A frequent point of confusion in the cladding industry is the distinction between fire stops and cavity barriers. While both serve to restrict the spread of fire, they have different primary functions and are governed by different sections of the Building Regulations. Cavity barriers are specifically intended to sub-divide large concealed voids, whereas fire stops are intended to seal specific gaps around penetrations or at the junctions of fire-separating elements.
Another misunderstanding relates to the "permanent" nature of fire stops. There is often an assumption that once a fire stop is installed, it requires no further attention. However, building movement, moisture ingress, or the subsequent installation of new utilities (such as fibre optic cables or air conditioning units) can compromise these seals. If a fire stop is breached to allow a new pipe or cable through, it must be professionally resealed using a system that is tested for that specific application.
Technical Specifications and Materials
The performance of fire stopping systems is verified through British Standards (BS) or European Standards (EN), such as BS 476 or BS EN 1366. These tests evaluate how long the system can prevent the passage of flame and smoke. The materials used vary significantly depending on the gap size and the movement expectations of the building.
| Material Type | Typical Application | Movement Capability |
|---|---|---|
| Intumescent Sealants | Small gaps around pipes or cables | Low to Moderate |
| Ablative Coated Batts | Large openings in walls or floors | Limited |
| Fire-Rated Mortar | Load-bearing seals in floor breaches | None |
| Fire Silicons | Linear joints in curtain walling | High |
Related Terminology
To accurately navigate technical reports regarding external walls, it is necessary to understand terms that are closely related to fire stops:
- Cavity Barrier: A component provided to seal a void to inhibit the pathway for fire and smoke.
- Intumescent: A substance that swells as a result of heat exposure, increasing in volume and decreasing in density to seal gaps.
- Compartmentation: The division of a building into fire-resisting cells to prevent the spread of fire from the area of origin.
- Linear Joint Seal: A specific type of fire stop used where two fire-separating elements meet, designed to accommodate structural movement.
- Service Penetration: Any hole made in a fire-separating element for the passage of pipes, cables, or ducts, requiring a fire stop to maintain the element's integrity.
In summary, fire stops are a non-negotiable element of the building's safety architecture. During any cladding testing, repair, or replacement project, the inspection and, if necessary, the reinstatement of these systems is a fundamental technical requirement to ensure the building fabric performs as intended under fire conditions.
Fire Stops