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Flexible Foiled Cavity Barrier (WB & VWB)

Product 55


[WB & VWB]

Flexible foiled moisture-resistant barrier for brick cavity

Not available to purchase online.

We need to ask you a few more questions and ensure this is the suitable product for your needs.

To order please call us on +44 (0) 1 304 842 555

£0.00 ex. Vat



Flexible Barrier for Brick Cavity

Flexible foiled barrier for brick cavity consisting of an intumescent strip faced with high tensile foil, ensuring optimum durability and moisture protection. The powerful intumescent seal, in the event of a fire, expands to create a powerful fire and smoke seal, thus providing effective fire protection. Additionally, a flexible mesh structure offers enhance robust strength and flexibility to the barrier section.

  • WB Cavity Barrier – thin flexible foil-faced intumescent strip. Fixed in a horizontal position in a brick/ block cavity. Fixed with mortar.
  • VWB Cavity Barrier – supplied with airflow system, either one, two, or three rows of holes. Dependant on the width of the barrier.
  • VWBG Cavity Barrier – supplied as a self-draining and airflow system. Fixed tubes into the barrier unit, set into the mortar allowing all moisture to drain to the external area. Also allowing free airflow into the cavity area where smoke sealing is required.

When ordering specify the overall cavity size as well as the required ventilation gap.

Cavity Barriers are pieces of fire-stopping material. They fit within the cavity of a building at each floor horizontally and party wall in a verticle position. The material provides compartmentation. Both the flames and heat cannot be transferred to other compartmental areas. Throughout the life of the building, the Cavity Barrier will remain fixed in place. In the event of a fire, the intumescent material expands and seals off the gaps. Additionally, the horizontal barriers allow for a ventilation gap within the cavity. Subsequently closing when the intumescent expands.

Our Cavity Barrier range at Envirograf® offers superb protection to your building by providing fire stopping. Explore the Cavity Barrier range online.


– All barriers in the range are designed to fix across the gap between the inner and outer course of brick to block or block to block walls
– The WB foiled cavity barrier range is designed to be fitted horizontally between brick or block walls, expanding to form a complete fire and smoke barrier in a fire
– Foiled cavity barriers are designed to allow insulation material to be installed both above and below the barrier
– VWBG barrier is self-draining – ideal for allowing free air flow in and out of cavities where smoke sealing is required
– The WBS flexible sponge barriers can be fitted horizontally or vertically between brick or block walls, resisting fire and smoke. The ventilated version, which must be fitted horizontally, is also fitted with an intumescent strip which expands to fill ventilation holes in a fire
– Sponge cavity barriers provide their own thermal insulation, but also allow for insulation material to be installed above and below the barrier
– Tested to BS EN 1363-1 1999, achieving up to 132 minutes fire protection.

Application Instructions

The barrier is held into the horizontal position by sandwiching it between the bricks and mortar at the
build stage. For vertical fix using clout nails.

The barrier is tucked into the brick mortar during build stage, It is then held and fixed to the wooden partition by being pushed into position , because the barrier is flexible it has spring tension and will hold its self in position.


The cavity barrier can be attached to the concrete/steel by means of a metal fixing strap FB/c1 1250mm long or FB/c2 2500mm long available from ENVIROGRAF with appropriate fixings The cavity barrier can be formed to the desired profile / shape so that when the cladding is fitted there is sufficient pressure to arch the barrier and form a fire break.


General Fixing Notes
Fix the metal straps with suitable steel fixings or hilti gun.
If the cavity barrier needs to be cut foil tape should be applied to the cut area.
Foil tape can be purchased separately quoting product code ST50

Order References / Sizes

WB Cavity Barriers                   Vertical & Horizontal

Non-ventilated            1 metre length &  2 metre length

Ventilated                   1 metre length  &  2 metre length

WB & VWB are made exact to the width flat. Should you need fixing to face of timber or brick etc. we can make them with a 30mm upstand and washers