• Envirograf WB & VWB Cavity Barrier

Envirograf WB Non-Ventilated Cavity Barrier

Product 55 - WB

We no longer stock this product, but can recommend Tenmat NVFB Non-Ventilated Fire Barrier as our nearest alternative. Please contact our Technical Team on 0113 2455450 (option 2) or send a message to [email protected] prior to purchase/use for advice on suitability.



WB Non-Ventilated Cavity Barriers for between brick or block walls. Upstand varieties can be made to order. Features intumescent that expands in fire, sealing gaps.

  • Refer to sizes below
  • Fit vertically & horizontally
  • 1m & 2m lengths
  • Use around window frames & door frames
  • Ideal for UPVC windows & timber-framed houses
  • Up to 2 hours fire protection


Available in 1 metre and 2 metre lengths


Ref Width
WB80 80mm
WB120 120mm
WB150 150mm
WB200 200mm
WB250 250mm

Made To Order

A 30mm upstand with washers can be made to order for fixing to inner-wall faces of timber, brick, etc, on barriers up to 250mm wide - please contact our sales team on 0113 245 5450.

Envirograf WB Non-Ventilated Cavity Barriers prevent the spread of fire and smoke through cavity walls. These flexible 4mm foiled barriers allow insulation to be installed above and below them, held in the mortar joint across an inner and outer course of brick and block or block to block. Use them horizontally or vertically, around window frames and door frames, and in timber-framed houses.

The barriers have intumescent material which expands during fire, sealing gaps to contain fire and smoke for up to 2 hours. By containing fire and smoke, the barriers allow for more evacuation time and can help prevent further damage to other rooms and buildings.

A ventilated (VWB) cavity barrier is also available and allows movement of moisture and air through the barrier, sealing up in fire.


A 5mm thick, foil clad intumescent (WB) which allows moisture to disperse, in various widths and up to 20mtr in length.

Used on both the vertical and horizontal faces around window frames and door frames.

For Brick & Block Cavities

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.

For Brick/Wooden Cavities

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.

For Concrete to Steelwork & Steelwork to Steel Frame

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
For continuous lengths, the cavity barrier should be overlapped by 50mm


  • Fully flexible
  • Easy to install
  • Up to 132 minutes of fire protection
  • Maintenance free
  • Moisture resistant

Material Specification:

This Product is made from the following materials:

  • Wire Mesh
  • Intumescent Material
  • Foil Tape
  • Craft Paper

Data For these materials can be found in the Health & Safety Data Sheet

Test Details:

Test Integrity Insulation
Warrington 169542 132 Mins 23 Mins
Chiltern IF 96019 107 Mins N/A

Envirograf Fire Cavity Barriers should be fitted by experienced professionals to ensure they are installed correctly. Products can only be guaranteed by Envirograf if fitted correctly and incorrect installations will be condemned if inspected. Check labels, fixing brackets, manufacturer installation instructions, etc. Should a site visit be required to check installation, this can be arranged upon request but will be chargeable.

IMPORTANT FIRE PRODUCTS NOTICE: The information displayed on this website should be used as a guide ONLY and our Technical Department should be contacted to obtain a tailored specification and any advice necessary before you place an order for fire protection products. Fire protection products are non-returnable except in accordance with Condition 8 of the Terms and ConditionsWe will not be held liable for any resulting damage to property, human life or monetary costs incurred due to the incorrect specification you have prepared or use of fire protection products caused by your negligence, including your failure to have contacted us to obtain the relevant advice/specification.

Any Envirograf products to be used in or for Harrods department store should be authorised with our Technical Team prior to purchase.

Product Details
Product 55 - WB

Customer agrees that before placing an Order, Customer has read and understood the most up to date Product Data Sheet for the Product. Where we have access to the Product Data Sheet from the manufacturer, we will either provide a copy on request, or include a link to the Product Data Sheet available on the manufacturer’s website. Customer further agrees that we have no liability for any errors or omissions contained within the Product Data Sheets. For more information, please see our Terms & Conditions of Sale.

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