What Is Fire Stopping? Fire Compartmentation Explained
Fire stopping and fire compartmentation are two of the most important — and most misunderstood — parts of passive fire protection. This guide explains what they are, how they work together, the methods and materials involved, and why getting them right is a legal requirement.
In short: Fire compartmentation divides a building into fire-resisting boxes. Fire stopping seals every gap and penetration in those boxes so fire and smoke cannot leak through. Together they contain a fire to where it starts.
What Is Fire Stopping?
Fire stopping is the sealing of gaps, joints and openings in fire-rated walls, floors and ceilings so that fire and smoke cannot pass from one fire compartment to another. Every time a service — a pipe, cable, cable tray or ventilation duct — passes through a fire-resisting wall or floor, it leaves a gap. Left unsealed, that gap is a direct route for fire and smoke.
Fire stopping fills those gaps with tested systems that restore the original fire resistance of the wall or floor — typically 30, 60, 90 or 120 minutes.
What Is Fire Compartmentation?
Fire compartmentation is the design principle of dividing a building into separate fire-resisting compartments using fire-rated walls and floors. The aim is to contain a fire within the compartment where it starts for long enough to protect escape routes and allow people to evacuate. Compartmentation is the strategy; fire stopping is the detailed work that keeps each compartment sealed and intact.
Common Fire Stopping Methods
Service penetration sealing
Sealing around pipes, cables and cable trays where they pass through walls and floors, using fire batt, mastic, mortar or compound.
Intumescent pipe collars & wraps
Fitted around plastic pipes; they expand in heat to crush the melting pipe and close the opening.
Linear gap & joint seals
Sealing the movement joints between floors and walls, and head-of-wall gaps, with fire-rated mastic and backing.
Cavity barriers
Installed within concealed voids, ceilings and external wall cavities to subdivide them and stop hidden fire spread.
Fire Stopping Between Floors
Vertical fire spread between floors is especially dangerous, so floor penetrations and the floor-to-wall junction need particular attention. Services passing through a floor slab are sealed with fire batt and intumescent mastic, fire-rated mortar around dense groups of penetrations, or fire collars around plastic pipes. The system must be tested to the same fire-resistance period as the floor it protects, and installed exactly as the manufacturer's tested detail specifies.
Not All “Foam” Is Fire Stopping
Ordinary expanding foam is not a fire stopping material. Using it to seal a penetration in a fire wall is a common and dangerous mistake. Only tested, certified systems should be used. See our guide on whether pink expanding foam can be used as fire stopping.
Why Fire Stopping Matters
- Contains fire and smoke to the compartment where it starts.
- Protects escape routes and buys time for safe evacuation.
- Maintains the fire resistance designed into the building.
- Is a legal requirement under Building Regulations and the Fire Safety Order.
- Is routinely checked in fire risk assessments and compartmentation surveys.
Worried About Your Compartmentation?
Fyrup carries out fire stopping surveys, remedial works and certification across London.
Frequently Asked Questions
What is fire stopping?
Fire stopping is the process of sealing gaps, joints and openings in fire-rated walls, floors and ceilings so that fire and smoke cannot pass through them. Whenever a pipe, cable, duct or structural joint penetrates a fire compartment, the gap around it is sealed with tested fire stopping materials to restore the fire resistance of that wall or floor.
What is the difference between fire stopping and fire compartmentation?
Fire compartmentation is the overall strategy of dividing a building into fire-resisting compartments (using fire-rated walls and floors) to contain a fire to one area. Fire stopping is the detailed work that seals the gaps and penetrations in those compartment walls and floors. In other words, compartmentation is the system and fire stopping is what keeps it intact.
What are fire stops?
Fire stops are the seals and barriers installed in openings and gaps within fire-rated construction. They include intumescent sealants, fire-rated mortar and boards, fire collars and wraps around plastic pipes, cavity barriers, and fire batt and mastic systems around cable and duct penetrations. Each fire stop is a tested system designed to maintain the fire rating of the wall or floor it sits in.
How is fire stopping done between floors?
Fire stopping between floors seals the gaps where services pass vertically through a floor slab, and the linear gaps at the floor-to-wall junction. Common methods include fire batt with intumescent mastic, fire-rated mortar around dense penetrations, and fire collars around plastic pipes. The system used must be tested to the same fire-resistance period as the floor (commonly 60 minutes).
What materials are used for fire stopping?
Common fire stopping materials include intumescent sealants and mastics (which expand when heated), fire-rated mineral wool batt, fire-resistant mortar and compounds, intumescent pipe collars and wraps, fire pillows for temporary or re-enterable seals, and cavity barriers. The correct material depends on the substrate, the size of the opening and the type of service penetrating it — and must be a tested system.
Is fire stopping a legal requirement?
Yes. Building Regulations Approved Document B requires that openings in fire-separating elements are adequately fire stopped, and the Regulatory Reform (Fire Safety) Order 2005 places an ongoing duty on the responsible person to maintain fire compartmentation. Defective or missing fire stopping is one of the most common findings in fire risk assessments and compartmentation surveys.
Why does fire stopping matter?
Without effective fire stopping, every pipe, cable and duct passing through a fire wall becomes a hidden route for fire and toxic smoke to spread rapidly through a building. Proper fire stopping keeps fire contained within its compartment, protecting escape routes, buying time for evacuation, and limiting damage. It is one of the most cost-effective forms of passive fire protection.
Protect Your Compartment Lines
Fyrup delivers tested, certified fire stopping and compartmentation surveys across London — restoring and documenting the fire resistance your building was designed to have.