5 key differences between cavity barriers and fire stops
In modern construction, fire safety is paramount. Two critical elements used to prevent the spread of fire are cavity barriers and fire stops. While both play essential roles, they serve distinct purposes and are applied differently in building designs. Understanding the differences between these two systems is key to ensuring comprehensive fire safety in any structure. Let’s explore the five key differences between cavity barriers and fire stops.
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1. LOCATIONS IN THE BUILDING
Cavity barriers are installed in concealed spaces such as wall cavities, ceilings, and floors. These areas often contain voids where fire could spread unseen, making cavity barriers essential in controlling the movement of fire through these hidden pathways. For example, they can be found in roof voids, between floors, and within cavity walls, limiting the spread of fire in areas where utilities like wiring or insulation may be present.
Fire stops, on the other hand, are used to seal penetrations in fire-rated walls or floors. These penetrations can be openings created for services such as pipes, ducts, and electrical cables that pass through fire-resistant barriers. Fire stops are specifically designed to block these gaps, preventing fire and smoke from moving between different compartments of the building. They are typically applied where fire-resistance-rated walls and floors have been breached.
2. FUNCTIONS & PURPOSE
The main function of cavity barriers is to limit the spread of fire within cavities. They help to compartmentalise hidden spaces, preventing fire from travelling quickly through concealed areas like wall cavities and floor voids. By containing fire in its point of origin, cavity barriers delay its spread, allowing more time for evacuation and firefighting efforts. Their role is critical in slowing down the spread of both fire and smoke within the building’s hidden structures.
Fire stops are designed to maintain the integrity of fire-rated walls and floors. By sealing penetrations created by utility installations, fire stops prevent fire and smoke from passing through openings in these barriers. Essentially, fire stops help protect the fire-resistant properties of walls and floors, keeping fire contained within designated fire compartments. This is vital in limiting the spread of fire to other parts of the building.
3. MATERIALS USED
Cavity barriers are typically made from stone wool, which is a fire-resistant material, often combined with intumescent materials. These materials expand when exposed to heat, sealing any gaps that could allow fire to pass through. Other materials, such as flexible fire-resistant fabrics, are also used in larger cavity spaces where additional flexibility is required.
Fire stops, in contrast, use a variety of fire-resistant sealants, collars, or wraps. These materials are chosen for their ability to block fire from passing through penetrations. For example, intumescent collars can be installed around pipes that pass through fire-rated walls, expanding in the heat of a fire to seal the opening and prevent fire from spreading.
Cavity barriers must meet strict passive fire protection standards that are designed to limit the spread of fire in concealed spaces. They are particularly focused on hidden cavities in wall and floor structures, ensuring that these areas are compartmentalised. Cavity barriers are subject to regulations such as Building Regulations Approved Document B and specific fire safety standards depending on the building’s usage and design.
Fire stops are required to comply with stringent fire-resistance ratings that ensure the protection of fire-rated walls and floors. These ratings are based on the ability of the fire stop to maintain the integrity of these barriers for a specified period, often measured in terms of hours (e.g., 30, 60, or 120 minutes). Proven performance following test standards and methodology ensures that fire stops perform as intended during a fire emergency, limiting the spread of fire between fire compartments.
Cavity barriers are installed during the construction phase in areas where cavities exist, such as in cavity walls, floors, and roofs. Their primary purpose is to prevent fire from spreading through these hidden spaces. Cavity barriers are commonly found in commercial buildings, apartment complexes, and high-rise structures where concealed spaces need to be effectively compartmentalised.
Fire stops are used both in new builds and during renovations, specifically around penetrations like pipes, ducts, and cables that breach fire-resistant barriers. These stops are applied to maintain the fire resistance of walls and floors, ensuring that the fire compartmentalisation is not compromised by service installations. Fire stops are also critical in retrofit projects, where fire-rated walls and floors need to be restored after utilities have been installed.
Conclusion
Cavity barriers and fire stops are both essential components of a comprehensive fire safety strategy in buildings, but they serve distinct purposes. Cavity barriers limit the spread of fire in hidden spaces, such as wall cavities and roofs, while fire stops maintain the integrity of fire-rated walls and floors by sealing penetrations caused by utilities. By understanding these differences, builders and developers can ensure that both systems are installed correctly to provide maximum fire protection.
If you need further information, you can read our comprehensive guide to cavity fire barriers here.
FAQs
Cavity barriers are fire-resistant materials installed in concealed spaces like wall cavities, ceilings, and floors to limit the spread of fire within these voids.
Fire stops are used to seal openings in fire-rated walls and floors where utilities pass through, preventing fire and smoke from spreading between compartments.
Both are required based on the building’s fire safety design and regulatory requirements to ensure comprehensive fire protection.
Cavity barriers use materials like stone wool and intumescent strips, while fire stops rely on fire-resistant sealants, collars, and wraps to block fire at penetrations.
Yes, fire stops can be applied during retrofitting or renovations, ensuring that fire-rated walls and floors remain intact after utility installations.
