Quality.

    Fire stopping and compartmentation: what good looks like

    Cavity barriers, penetrations and compartment integrity.

    What good looks like

    Fire stopping and compartmentation: what good looks like

    Compartment lines that are continuous from slab to roof, cavity barriers where the cavity is interrupted, and every penetration reinstated to the fire resistance of the element it passes through.

    Compartmentation is a line, not a product. Trace it on a section: it starts at the separating floor or wall, continues past every service, and finishes at the underside of the roof covering. Anywhere the line is broken and not reinstated is where fire will pass. Cavity barriers do two jobs — they close the cavity at the edges of the compartment and they subdivide long cavities so fire cannot travel unseen. They must be tight to both faces of the cavity and mechanically fixed; a barrier that has sagged onto the wall ties is doing nothing. Service penetrations are the failure most often found late. Every pipe, cable, duct and riser through a compartment element needs a tested solution installed to the manufacturer's instructions, and photographed before it is covered.

    Basis in regulation

    Before you start

    Before you start: fire stopping and compartmentation

    Checks to clear before the compartment line is closed up.

    Mark the compartment lines on a marked-up drawing kept on site, and make sure the trades penetrating them can see it. Confirm the fire stopping products specified are tested for the exact substrate and service they will be used on — an intumescent collar approved for a masonry wall is not automatically approved for a plasterboard one. Agree a photographic record: every penetration photographed with a plot and location reference before it is boarded. Confirm cavity barrier positions at compartment junctions, openings and at the maximum subdivision spacing, and check the roof void barrier detail at the party wall before trusses are felted.

    Basis in regulation

    Key requirements

    Cavity Barriers and Fire-stopping Installation

    Cavity barriers and fire-stopping must be installed precisely according to the design and relevant Building Regulations to prevent fire and smoke spread within concealed spaces. Where these elements do not align with structural members, additional support must be provided to ensure a robust backing

    Cavity barriers and fire-stopping must be installed precisely according to the design and relevant Building Regulations to prevent fire and smoke spread within concealed spaces. Where these elements do not align with structural members, additional support must be provided to ensure a robust backing for their installation. Horizontal cavity barriers, particularly in masonry cladding, require DPC trays with an upstand to protect them from moisture.

    Basis in regulation

    Suitable fire-stopping materials

    The selection of fire-stopping material must be appropriate for the specific application and meet performance requirements. Common materials used for fire-stopping include rock fibre quilt, cement mortar, gypsum plaster, intumescent mastic or strips, and proprietary sealing systems. These materials

    The selection of fire-stopping material must be appropriate for the specific application and meet performance requirements. Common materials used for fire-stopping include rock fibre quilt, cement mortar, gypsum plaster, intumescent mastic or strips, and proprietary sealing systems. These materials are assessed to ensure they can effectively reinstate the fire resistance of a building element.

    Basis in regulation

    Service Installation in Fire-Resisting Walls

    Services in fire-resisting separating walls must be limited to those specified in the design, and their installation must not impair the fire resistance of floors or walls. Notching or drilling of structural timber members for services should strictly follow the design specifications, with any devia

    Services in fire-resisting separating walls must be limited to those specified in the design, and their installation must not impair the fire resistance of floors or walls. Notching or drilling of structural timber members for services should strictly follow the design specifications, with any deviations requiring designer approval.

    Basis in regulation

    Fire resistance of closed panel systems

    Closed panel systems must be designed to provide adequate fire resistance and effectively resist the spread of fire and smoke. This includes considering the fire performance of the panel units themselves, the correct installation of cavity barriers, fire-stopping, and the appropriate detailing aroun

    Closed panel systems must be designed to provide adequate fire resistance and effectively resist the spread of fire and smoke. This includes considering the fire performance of the panel units themselves, the correct installation of cavity barriers, fire-stopping, and the appropriate detailing around service penetrations.

    Basis in regulation

    Fire resistance of roof void access hatches

    Where an access hatch to a roof void is required to provide fire resistance, its construction must be supported by test evidence demonstrating the specified fire resistance period. This ensures the hatch contributes to the overall fire safety strategy of the building, preventing fire spread through

    Where an access hatch to a roof void is required to provide fire resistance, its construction must be supported by test evidence demonstrating the specified fire resistance period. This ensures the hatch contributes to the overall fire safety strategy of the building, preventing fire spread through the roof void.

    Basis in regulation

    Fire separation at eaves for attached garages

    Where an attached garage does not have a ceiling or a floor above it, vertical fire separation may be necessary at the eaves level to prevent fire spread. This ensures the garage's eaves cavity is closed off to the dwelling. Timber constructions require specific fire-stopping materials to achieve th

    Where an attached garage does not have a ceiling or a floor above it, vertical fire separation may be necessary at the eaves level to prevent fire spread. This ensures the garage's eaves cavity is closed off to the dwelling. Timber constructions require specific fire-stopping materials to achieve this separation.

    Basis in regulation

    Closing cavities in fire-resisting walls

    Fire-resisting walls constructed from masonry with a cavity must have the cavity closed at the top, typically at floor and ceiling junctions, to prevent fire spread within the void. Similarly, framed fire-resisting walls require cavity barriers at junctions with floors and ceilings to maintain compa

    Fire-resisting walls constructed from masonry with a cavity must have the cavity closed at the top, typically at floor and ceiling junctions, to prevent fire spread within the void. Similarly, framed fire-resisting walls require cavity barriers at junctions with floors and ceilings to maintain compartmentation.

    Basis in regulation

    Fire stopping at roof junctions

    Where separating or compartment walls meet pitched or flat roofs, effective precautions are essential to prevent fire spread into the roof space. This includes installing soft fire-stopping materials above and below the roofing underlay, allowing for roof movement while ensuring fire integrity.

    Where separating or compartment walls meet pitched or flat roofs, effective precautions are essential to prevent fire spread into the roof space. This includes installing soft fire-stopping materials above and below the roofing underlay, allowing for roof movement while ensuring fire integrity.

    Basis in regulation

    Firestopping for MVHR Systems

    Mechanical Ventilation with Heat Recovery (MVHR) ductwork penetrating fire-resisting elements must be firestopped to maintain the element's fire performance. This includes ensuring continuity of fire resistance in walls and floors, and the integrity of protected escape routes like stairs and halls.

    Mechanical Ventilation with Heat Recovery (MVHR) ductwork penetrating fire-resisting elements must be firestopped to maintain the element's fire performance. This includes ensuring continuity of fire resistance in walls and floors, and the integrity of protected escape routes like stairs and halls. The firestopping solution must be appropriate for the duct material and size, considering the specific building fire strategy.

    Basis in regulation

    Proprietary Fire Protection Component Specification

    Any proprietary passive fire protection products used in construction must be tested to relevant British or European standards. The specified product must match the actual site conditions and applications, ensuring its performance is validated for the intended use. This is crucial for maintaining th

    Any proprietary passive fire protection products used in construction must be tested to relevant British or European standards. The specified product must match the actual site conditions and applications, ensuring its performance is validated for the intended use. This is crucial for maintaining the fire integrity of building elements.

    Basis in regulation

    Fire-stopping for service penetrations

    Any services that penetrate fire-resisting elements such as floors, walls, or partitions must have appropriate fire-stopping installed. If a proprietary system, like an intumescent seal, is used, it must be fitted strictly according to the manufacturer's instructions to maintain the fire resistance

    Any services that penetrate fire-resisting elements such as floors, walls, or partitions must have appropriate fire-stopping installed. If a proprietary system, like an intumescent seal, is used, it must be fitted strictly according to the manufacturer's instructions to maintain the fire resistance rating.

    Basis in regulation

    Key requirements: fire stopping and compartmentation

    The requirements most often picked up when the compartment line is inspected.

    Separating walls and compartment floors achieving the required fire resistance, with no unfilled perpends or missed board layers. Compartment line continuous to the underside of the roof covering at the party wall. Cavity barriers at every compartment junction, around openings and at the maximum permitted subdivision spacing, tight to both faces and mechanically fixed. Service penetrations fire stopped with a tested system installed to the manufacturer's instructions, reinstating the full fire resistance of the element. Pipe penetrations within the permitted diameter or fitted with a tested sleeve or collar. Fire doors where the layout requires them, correctly hung with the specified gaps and intumescent seals. Photographic evidence captured before anything is covered up.

    Basis in regulation

    Cavity barriers in internal walls

    Internal walls of hollow or cavity construction, whether fire-resisting or not, require the installation of cavity barriers. These barriers must be placed at the perimeter of the cavity and at junctions with fire-resisting floors and other fire-resisting walls to prevent the unseen spread of fire an

    Internal walls of hollow or cavity construction, whether fire-resisting or not, require the installation of cavity barriers. These barriers must be placed at the perimeter of the cavity and at junctions with fire-resisting floors and other fire-resisting walls to prevent the unseen spread of fire and smoke.

    Basis in regulation

    Fire Integrity for Electrical Items in Fire Partitions

    All electrical components, including cables, conduits, sockets, and back boxes, installed within fire-rated partitions must comply with BS 7671 and maintain the partition's fire resistance. When using intumescent pads or lined backing boxes, they must be fire-rated for the intended application and i

    All electrical components, including cables, conduits, sockets, and back boxes, installed within fire-rated partitions must comply with BS 7671 and maintain the partition's fire resistance. When using intumescent pads or lined backing boxes, they must be fire-rated for the intended application and installed according to the manufacturer's instructions to preserve compartmentation.

    Basis in regulation

    Fire performance of light steel frame components

    The fire performance of light steel frame (LSF) walls, floors, and roofs must comply with Building Regulations, supported by appropriate test evidence to relevant British or European Standards. Design details, particularly around openings and critical junctions, should ensure the specified fire resi

    The fire performance of light steel frame (LSF) walls, floors, and roofs must comply with Building Regulations, supported by appropriate test evidence to relevant British or European Standards. Design details, particularly around openings and critical junctions, should ensure the specified fire resistance is maintained.

    Basis in regulation

    Fire resistance details for attached garages

    Walls and ceilings separating an attached or integral garage from a dwelling must achieve a minimum fire resistance rating, typically REI 30. This can be achieved using fire-resisting masonry, studwork, or floor/ceiling constructions, with all junctions adequately fire-stopped. Any door between the

    Walls and ceilings separating an attached or integral garage from a dwelling must achieve a minimum fire resistance rating, typically REI 30. This can be achieved using fire-resisting masonry, studwork, or floor/ceiling constructions, with all junctions adequately fire-stopped. Any door between the garage and the home must be a fire door, fitted with a self-closing device, complying with fire resistance requirements.

    Basis in regulation

    Critical dimensions at this stage

    Browse all critical dimensions
    England
    Low-rise traditional

    Original editorial guidance based on publicly available Approved Documents. Not building control approval, a warranty determination, or a substitute for the full source document.

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