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Flexible Cavity Barrier Range

Product 55


[ WB ] [ WBS ]

Flexible, moisture resistant barriers for use in brick wall cavities

Not available to purchase online.

Please contact us on +44 (0) 1 304 842 555 to order.



A range of flexible, moisture-resistant cavity barriers for providing an effective fire and smoke seal in the cavity between brick or block walls.
WB Flexible Foiled Cavity Barriers

A barrier consisting of an intumescent strip faced with high tensile foil, which expands to create a powerful fire and smoke seal. Available in a ventilated form with one, two or three rows of holes, depending on the width of the cavity.

WBS Flexible Sponge Cavity Barriers

An intumescent impregnated sponge barrier with fire and smoke stopping capabilities. Available in a ventilated form fitted with a rubberised intumescent strip which expands in a fire to fill the ventilation holes.


– 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

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


WBS Cavity Barriers

Ventilated fireproof sponge for cavities
Cavity width allow when ordering 10mm wider for compression in cavity.
You can have one or 2 ventilation holes : A 1 hole B 2 holes

Cavity Width        Actual Width     Sponge Thickness
of sponge
VWBS80          80mm         90mm           40mm       Hole type A
VWBS135      135mm      145mm           40mm       Hole type A or B
VWBS165      165mm      175mm           40mm       Hole type A or B
VWBS210      210mm       220mm          40mm       Hole type A or B
VWBS265      265mm       275mm          40mm       Hole type A or B

Cavity Width       Actual Width      Sponge Thickness
of sponge
WBS80           80mm          90mm          40mm
WBS135      135mm        145mm          40mm
WBS165      165mm        175mm          40mm
WBS210       210mm       220mm          40mm
WBS265       265mm       275mm          40mm