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Fire stopping is the process of sealing openings, joints and gaps in fire-resisting walls and floors so that fire and smoke cannot easily pass from one part of a building to another.
These openings are commonly created when pipes, cables, ducts and other building services pass through a wall or floor. Unless the opening is protected with a suitable fire-stopping system, it can undermine the fire resistance of the entire building element.
Fire stopping is therefore an essential part of passive fire protection. Unlike alarms, sprinklers and extinguishers, passive fire protection does not need to be activated. It is built into the structure and is intended to contain fire for a specified period, supporting safe evacuation, firefighting operations and property protection.
This guide explains how fire stopping works, where it is required and what building owners, designers and contractors should consider when specifying, installing and maintaining it.
Many buildings are divided into fire-resisting areas known as compartments. Compartment walls and floors are designed to restrict the spread of fire and smoke for a defined period.
However, a compartment is only effective when the barrier is complete.
Mechanical, electrical and plumbing services regularly pass through compartment walls and floors. Every penetration creates a potential route through which flames, hot gases and smoke may travel.
A fire-stopping system reinstates the required performance around that opening. Depending on the application, it may:
The system must be suitable for the complete arrangement, not just the product in isolation. The substrate, opening size, penetrating service, insulation, supports, seal depth and orientation can all affect performance.
The terms are related, but they are not interchangeable.
Compartmentation is the wider strategy of dividing a building with fire-resisting walls and floors. It helps contain fire within a defined area.
Fire stopping protects joints and openings that would otherwise breach those fire-resisting elements.
Cavity barriers restrict the concealed spread of fire and smoke within cavities, such as voids behind external wall systems, suspended ceilings or roof spaces.
Fire stopping supports compartmentation; it is not another name for the entire compartmentation system.
For example, a concrete floor may provide a fire-resisting boundary between two storeys. If a plastic soil pipe passes through it, the surrounding penetration may require a tested fire collar or other suitable system. The floor is the compartment element, while the protection around the pipe is the fire stop.
Correctly designed and installed fire stopping helps:
The Health and Safety Executive warns that compartments with unprotected openings may fail during construction as well as after completion. Its construction fire-safety guidance states that openings should be protected to an equivalent standard of fire resistance to the rest of the compartment. Read HSE publication HSG168.
A small gap can therefore have consequences far beyond its physical size.
Fire stopping may be needed anywhere an opening or joint affects a fire-resisting element. Common locations include:
The need for fire stopping should be established from the building’s fire strategy and compartmentation drawings. Applying fire-resistant material to every visible gap is not a substitute for identifying which walls and floors form fire-resisting boundaries.
There is no universal product that can protect every type of opening. A compliant solution is normally selected from a tested or appropriately assessed system that matches the actual site conditions.
Fire-rated sealants may be used around certain small penetrations and linear joints. Some products are intumescent, meaning they expand when exposed to heat.
The correct seal depth, backing material, annular gap and substrate are critical. A fire-rated label alone does not make a sealant suitable for every application.
Fire batt commonly consists of a high-density mineral fibre board with a fire-resistant coating. It can be cut and installed around multiple services within an opening.
The tested arrangement may also require specific sealants, collars or pipe-closing devices. The maximum opening size, service spacing and permitted supports must be checked against the system evidence.
Fire collars and wraps are generally used with combustible pipes. Their intumescent material expands under heat, helping close the void left as the pipe softens or melts.
Suitability depends on factors including:
A collar tested with one pipe material or wall type should not automatically be assumed to work with another.
Fire sleeves may be used around specified pipes, cables or ventilation services. Their intended application and performance vary between manufacturers, so the system details must be checked carefully.
These systems can be useful where services may change, such as data and communications installations. They must still be fitted in accordance with the tested configuration, including the permitted opening size, service type and compression requirements.
Specialist mortars may be used for larger openings, particularly through rigid walls and floors. Services passing through the mortar may require additional protection.
Linear joint systems protect gaps between fire-resisting construction elements. They may need to accommodate movement while maintaining integrity and insulation performance.
Approved Document B specifically recognises that fire stopping around pipes and ducts may need to allow for thermal movement.
Where ductwork crosses a fire-resisting element, a damper or fire-resisting duct system may be required. The surrounding opening must be protected using details compatible with the damper, duct, supporting construction and manufacturer’s instructions.
Fire-safety legislation and technical guidance differ across the UK. The following overview concentrates on England; projects in Wales, Scotland and Northern Ireland should be checked against their respective regulations and guidance.
Requirement B3 of the Building Regulations addresses internal fire spread through the building structure. Approved Document B provides guidance on ways of meeting the functional requirements in common building situations.
Its fire-stopping provisions say that:
The latest editions and amendments should always be checked on the official Approved Document B page.
Approved Documents are statutory guidance rather than a universal specification for every building. Complex or unusual projects may need a fire-engineered, evidence-based approach agreed with the relevant design and building-control professionals.
England’s building regulations place duties on clients, designers and contractors involved in building work. They must plan, manage and monitor their work so that it complies with relevant requirements.
People and organisations undertaking fire-stopping design or installation should have the necessary competence and organisational capability. The person making an appointment must also take reasonable steps to establish that the appointee is competent.
The Building Safety Regulator provides a detailed overview of these building-regulation dutyholder and competence requirements.
For occupied non-domestic premises and relevant parts of residential buildings in England and Wales, the Regulatory Reform (Fire Safety) Order 2005 places duties on the Responsible Person. These include undertaking a suitable fire-risk assessment and maintaining fire precautions in an efficient state, efficient working order and good repair.
Fire stopping and compartmentation should therefore be considered throughout the building’s life, not only at practical completion. View the Fire Safety Order.
Regulation 38 of the Building Regulations requires relevant fire-safety information to be provided to the Responsible Person when applicable building work is completed.
For higher-risk buildings in England, additional requirements apply to the creation, maintenance and sharing of digital building information. Inspection records, maintenance information and evidence of building changes can form part of this golden thread. Read the government’s golden-thread guidance.
Compliance cannot be established simply by checking that red sealant or a fire-rated product is present.
A fire-stopping detail should be supported by evidence covering the actual installation. Important variables include:
Where site conditions fall outside the tested scope, the issue should be referred to a competent designer, fire engineer, manufacturer or other appropriate specialist. Products from different systems should not be mixed without suitable supporting evidence.
The Association for Specialist Fire Protection’s technical publications include guidance on penetration seals and other forms of passive fire protection. Explore the ASFP technical documents.
A reliable process begins before installation.
Review the fire strategy, drawings and specifications to determine where compartment walls, floors, protected routes and other fire-resisting elements are located.
For each relevant opening, record the substrate, service type, dimensions, insulation, support arrangement and required fire performance.
Choose a tested or appropriately assessed detail whose field of application covers the site conditions. Confirm that all specified components are compatible.
Fire stopping often involves several trades. Poor sequencing can result in inaccessible openings, unsupported services or later damage to completed seals.
The installer should follow the relevant specification, evidence and manufacturer’s instructions. Surfaces must be prepared correctly, and required depths, spacings, fixings and backing materials must be achieved.
Installations should be checked while they remain accessible. Photographic records are most useful when they show the opening before work, the components during installation and the completed seal.
A traceable record might include:
Later contractors must not cut through, remove or modify a fire stop without reviewing and reinstating the system appropriately.
Frequent problems include:
Many defects begin before the installer arrives. Poor design coordination, late service changes and a lack of accessible system details can make compliant installation considerably harder.
There is no single inspection interval suitable for every building. The programme should reflect the building’s fire-risk assessment, use, condition and likelihood of alteration.
Inspection should also be considered:
A compartmentation or passive-fire survey can help locate defects, but its scope should be clearly defined. The surveyor needs to understand the fire strategy and distinguish genuine breaches of fire-resisting construction from openings in elements that do not form compartment boundaries.
No. Fireproofing is a broad term covering methods used to protect materials or structures from fire. Fire stopping is the specific protection of joints, gaps and penetrations in fire-resisting construction.
No. Compartmentation is the division of a building using fire-resisting elements. Fire stopping helps maintain those elements where they have joints or openings.
Ordinary expanding foam should not be treated as fire stopping. Even a product marketed as fire-rated is only suitable where its supporting evidence covers the precise wall, floor, joint or penetration arrangement.
Fire stopping is required where an opening breaches an element that must provide fire resistance. The fire strategy and compartmentation drawings should be used to identify those locations.
Other openings may require protection for different reasons, but covering every service hole with sealant is not a substitute for a properly designed system.
Responsibility can involve several parties, including the client, designers, principal designer, principal contractor, specialist contractor, building owner and Responsible Person. Their particular duties vary with the project stage and applicable legislation.
Clear design ownership, competent appointments, coordination and accurate handover information are essential.
The required period depends on the building, location, use and fire strategy. Ratings such as 30, 60, 90 or 120 minutes are commonly encountered, but they should never be selected by assumption.
The fire stop must provide the performance required for the element and the relevant application.
Effective fire stopping depends on more than selecting a fire-rated product. It requires coordinated design, competent installation, inspection and a traceable record of what has been installed.
[Company name] provides [fire-stopping design, installation, inspection and remediation services] for [target sectors or locations].
To discuss a new project, existing-building survey or remedial programme, [contact our fire-stopping team] or call [telephone number].
This article provides general information and is not a substitute for project-specific fire engineering, legal advice or review by a competent professional.
