What Is a Cavity Barrier?

Cavity barriers are blocks of fire-resistant material used to seal off empty spaces within a building in order to prevent the spread of fire. These spaces, known as cavities, are typically found within walls and are surrounded by different building elements. They do not serve any specific function and can act as pathways for smoke, hot gases, and flames to move from one part of the building to another.

It's crucial to install effective cavity barriers within concealed voids in roofs, ceilings, floors, and walls to prevent the spread of fire within the building. In the event of a fire, the fire-resistant material within the cavity barrier will expand and seal off these spaces, preventing the spread of flames and smoke.

Cavity barriers usually consist of intumescent materials and are installed vertically at every party wall and horizontally at every floor to compartmentalize the building in the event of a fire. It's important to make sure that the barriers remain effective throughout the building's lifespan, considering any potential building movements such as shrinkage or subsidence.

Why is Cavity Barrier Installation Important?

Cavity barriers are inert fire protection components that prevent smoke and flames from spreading through walls. They work by closing off spaces in a cavity when a fire breaks out. This is possible because the materials of cavity barriers are sensitive to extreme temperatures and will expand when exposed to fire.

Slowing down a fire is the first step to protecting your premises when a fire occurs. It gives occupants enough time to evacuate and minimizes property damage to other parts of the building. It also helps fire and rescue services gain a foothold in extinguishing the fire.

Horizontal and vertical cavity barriers to divide and compartmentalise hidden cavities, the spread of fire from one area of the building to another is prevented.

It is essential for all building companies to install cavity barriers during construction since they are a necessary fire protection component for every building in the UK. It's important to note that older buildings may not have been constructed to meet this standard or may have been built before this requirement was mandatory. As a result, it's essential to have the cavity barriers reviewed as part of the fire risk assessment

Cavity barriers must be installed as per Approved Document B :

- At the point where each compartment wall and compartment floor meets the exterior cavity wall (excluding walls with two masonry leaves or concrete with at least 75mm thickness).

- At the point where an interior wall (excluding walls with two masonry leaves or concrete with at least 75mm thickness) meets each compartment wall, compartment floor, or other door or wall construction that can act as a fire-resisting barrier.

The purpose of installing cavity barriers is to isolate one compartment from another in order to prevent the spread of fire from one area to another.

What is the Difference Between a Cavity Barrier and a Fire Stop?

A fire stop is an inert fire protection component that is used to close or seal gaps or openings between fire-resistant building features, such as compartment walls or floors, or at junctions or joints in the fire protection system. It's important to note that a fire stop must provide the same level of resistance and insulation to the passage of smoke and flames as the building components in which it is installed.

Cavity barriers are used to close hidden gaps and prevent the spread of flame or smoke, helping to curb the spread of fire. They are typically installed in ceiling voids and cavity walls during building construction.

According to Approved Document B and BS 9991, cavity barriers must have a minimum insulation of 15 and a minimum integrity of 30.

It is important to ensure that both fire stops and cavity barriers are positioned and fitted correctly according to the manufacturer's specifications. This involves using suitable materials for the spaces that need to be closed.

Distinguishing Between Cavity Barriers and Cavity Closers:

Cavity barriers are intumescent substances used to seal cavities and voids in buildings, preventing the movement of fires through the cavity to other parts of the building.

On the other hand, cavity closers are used to seal cavities, but they mainly consist of an insulated trim or closer that is not fireproof. Their purpose is to prevent dampness and exterior water vapor from entering the cavity wall. They are not intended to stop fires from spreading. However, if a cavity closer uses a fire-retardant material, it would be considered a cavity barrier.

In conclusion, all cavity barriers should be designed and fitted in a way that ensures optimal performance. They should be mechanically installed tightly into position in a rigid construction, or ideally fire-stopped at a joint between itself and the assembly to which it is being fitted, such as sheeting, tiles, or slates. Additionally, the risk of fittings failing during a fire should be taken into consideration.