Wall Cavity Fire Barrier - Red Edition

Fire and Smoke Barrier for masonry cavity walls.

AIM Wall Cavity Barrier

Red Edition tested to BS EN 1366-4 is available for new projects from July 1st 2024

Blue foil remains available for completion of projects to BS 476-20/BS 476-22


AIM Wall Cavity Barrier is made from foil faced high density, compressible, Rockwool stone wool and is suitable for use in all masonry cavity walls. The barrier prevents the passage of heat, flame and smoke within the cavity it fills for 30, 60 or 120 minutes.


AIM Wall Cavity Barrier may be used to provide a fire barrier in masonry cavity walls as well as for fire stopping between a masonry wall system† and a concrete floor slab. It is typically used vertically and horizontally to provide a fully closed cavity fire barrier along compartmentation lines in the outer leaf of the building. AIM Wall Cavity Barrier may be used in different or non-standard constructions, such as rainscreen cladding systems, with the approval of a competent person.
† AIM Wall Cavity Barrier has not been tested for use with aluminium curtain wall systems.


  • High density foil faced stone wool barrier.
  • Thicknesses to provide 30, 60 and 120 minute fire ratings.
  • For use within voids up to 600mm.
  • Tested for use with SFS substrate.
  • Tested for use with Masonry Support brackets.
  • Available cut to size or in slab form for on site cutting.
  • Reduces airborne transmission of sound by a minimum of 21dB RW.
  • Jointing tape not required.
  • Suitable for horizontal and vertical use.
  • Suitable for use with all thermal insulation types


  • Reduces airborne sound through the external wall cavity.
  • The product provides 30, 60 or 120 minutes Integrity & Insulation when tested to EN 1366-4.
  • Can be used in a wide variety of construction types, with the correct approval.



AIM Wall Cavity Fire Barrier cut to size

Length: 1000mm
• Thicknesses: 75mm, 100mm, 125mm
• Foil Facing (with AIM logo now in red print to denote new test results)
• Cavity widths: 50 - 600mm (barrier to be compressed by 5%)
• Pre-compressed for ease of installation
• Faced with reinforced aluminium foil for enhanced smoke resistance

PACKAGING (cut product)

AIM Wall Cavity Barrier are generally packed into cartons and stretch wrapped onto wooden pallets with a showerproof polythene pallet cover and high quality edge protectors.

AIM Wall Cavity Fire Barrier Slab

• Slab thickness: performance (integrity and insulation)
• 75mm: 30 minutes
• 100mm: 60 minutes
• 125mm: 120 minutes
• Slab size: 1000 x 600mm and 1000 x 1200mm
• Foil facing imprinted with AIM logo now in red print to denote new test results
• Available polythene sleeved when supplied pre-cut to size*

PACKAGING (Slab product)

Orders for slab and half slab barrier will be supplied stretch wrapped onto pallets with a showerproof polythene pallet cover and edge protection (ie, no cartons).


AIM Wall Cavity Barrier is supplied either cut to size, complete with appropriate clips or in slab form with clips sold as separate items to quantities determined by the installer.
Wall Cavity Fire Barrier complete with DPC


Can be supplied with a DPC, either loose or pre-laminated. The DPC variant has been fire tested to EN 1366-4.

Barrier in a polythene sleeve*

*This product variant is available but has not been fire tested. It's use would be subject to the approval of the project fire engineer or consultant



AIM Wall Cavity Barrier has been Tested to EN 1366-4. Full details of the scope of tested evidence is shown in
the table below

Masonry to Masonry ConstructionSFS to Masonry Construction
ThicknessIntegrity / Insulation up to 400mm Cavity Integrity / Insulation up to 600mm CavityMasonry Support BracketIntegrity / Insulation up to 300mm Cavity
75mm120 / 30 minute 60 / 30 minutesN/AN/A
100mm120 / 60 minutes60 / 60 minutes120 / 60 minutes120 / 60 minutes*
125mm120 / 120 minutes120 / 90 minutes120 / 120 minutes*120 / 120 minutes*
Test ReportsWF 522952 (V)
WF 523632 (H
WF 533341 (V)
WF 399340 (H)
WF 537195 (H)WF 538665 (V)
WF 538666 (H)
Third Party CertificationIFCC 1897N/AN/AN/A
* Results achieved with A1 stone wool insulation fitted above and below the seal.
(V) vertical installation, (H) horizontal installation. Performance is related to barrier thickness.
Cavity SizeFixing Clip RequiredClip gaugeFixing Frequency
Up to 160mmSmall Fixing Clip25mm x 0.9mm2 per metre (min 2 per cut length) @ 500mm
161mm to 400mmLarge Fixing Clip25mm x 1.2mm2 per metre (min 2 per cut length) @ 500mm
401mm to 600mHD Fixing Clip25mm x 1.6mm3 per metre (min 2 per cut length) @ 333mm


In general, AIM Wall Cavity Barriers are used in conjunction with AIM's OSCBs. The AIM Wall Cavity Barriers tend to be used for vertical fire stopping and permitting free flowing ventilation through the cavity in a horizontal plane. Wall Cavity Barriers provide a fully filled cavity solution and are generally used vertically to prevent the spread of fire across the face of a building

AIM Wall Cavity Barriers provide a fully filled cavity solution and are typically used vertically and horizontally, sealing the cavity along compartmentation lines to ensure a continuous fire barrier in the building’s outer leaf within masonry constructions, especially where a more stringent fire resistance is required. AIM Wall Cavity Barrier has also been tested for use as a cavity closer around door and window openings.

The barrier prevents the passage of heat, flames and smoke through the external wall cavity for periods of 30, 60, or 120 minutes in a fire situation. It also reduces flanking sound transmission through external wall cavities. AIM Wall Cavity Barriers are available either cut to size or in slab format for cutting on site.

The AIM Wall Cavity Barrier has been tested in conjunction with Leviat brick support shelfs where the location of the barrier and brick support shelf coincides. The AIM Wall Cavity Barrier has been tested with and without thermal insulation and with the fins fully exposed. The table and drawings below show the relative position of the brackets and the fire resistance that is achieved with the respective barrier thickness

WCB ThicknessBarrier PenetrationSW Thermal InsulationIntergrity (Minutes)Insulation (Minutes)

* Only 1 hour where the barrier is fully penetrated and no stonewool thermal insulation


AIM Wall Cavity fire Barrier is friction fitted into place in conjunction with fixing clips; it must fit tightly and completely fill the cavity with 5% compression. If the barrier is also being used to prevent air leakage, it requires taped joints and intumescent mastic to the linear edges to create a seal. 


Clips are required when the barrier is installed. Two clips per length are required for cavities up to 400mm.
For cavities 401mm to 600mm, three fixing clips are required per length. Clips are supplied as flat strips, pre-notched to allow them to be easily formed on site and with pre-stressed snap off points to enable the correct length to be created.
Clips must not be installed with the sharp points left exposed at any time, due to risk of serious injury.
For horizontal slab edge applications the fixing clips should penetrate the barriers width by approximately 75% and mid height. Fixing clips may be secured to the edge of the concrete slab or the top surface of the slab by forming the clips to a Z shape. The cavity barrier may be located at the top, bottom or mid-height of the floor slab.

For vertical applications the fixing clips should penetrate the barriers width by approximately 75% and mid width of the seal. The fixing clips may be secured to the substrate on either side of the cavity barrier.
If the cavity barriers are installed in advance of the façade, it may be necessary to secure the cavity barrier to the substrate to prevent it becoming dislodged in high winds. The joints between adjoining sections, and where horizontal and vertical cavity barriers intersect, must be tight and secure without any gaps or voids.


If the gap to be filled is between two building components which might separate in a fire, the two components must be mechanically linked so that separation cannot occur.

Masonry Cavity Walls

Horizontal Barrier: Bed the fixing clips into the joints in the internal leaf. A damp proof membrane or cavity tray must be installed into the cavity wall immediately above, and to the outside of, the fire barrier.


• PPE abrasion resistant gloves
• PPE impact resistant goggles
• RPE dust mask
• Sharp knife
• Tape measure
• Insulation saw
• Acrylic fire rated intumescent mastic (optional extra)


Cut product is supplied in cartons on pallets, slab products are supplied on wooden pallets with edge protection and a shower proof hood. Products should be stored away from the elements until ready for installation.


This product does not contain moving parts and, if undisturbed in the cavity, requires no routine inspections or maintenance.
It is recommended that the integrity of the barrier is rechecked if further works are carried out, which may involve disturbing the product.


AIM fire barriers are chemically inert, will not sustain vermin and do not encourage the growth of rot, fungi, moulds or bacteria. They are compatible with all normal building materials. Rockwool stone wool has been proven in service for over 60 years, in a wide range of climates and degrees of exposure. It will generally perform effectively for the lifetime of the building, plant or structure.


Insulation products supplied by AIM are considered to be inert articles and as such are exempt from requirements to provide a Safety Data Sheet.
A Product Safety and Handling Information Sheet is available upon request.


Global warming potential = zero

The stonewool element of the products originate from Rockwool UK. It may be possible to recycle clean and uncontaminated material under Rockwool UK’s Rockcycle® service. Please contact Rockwool on 01656 868400 for further details.


To order this product the following information will be required:
• Cavity depth in mm
• Fire Performance required
• Approximate quantity
• Delivery location
All AIM fire barriers are made to order. Products are typically supplied in seven to ten working days but lead times may vary depending on existing factory commitments.
There is no minimum order quantity or value although small orders may attract transport surcharges.


Technical Support is available from our experienced sales team on 01293 582 400 or [email protected]


AIM are a quality insulation convertor with over 30 years experience in the design, testing & manufacturing of high quality fire barriers for customers worldwide.

Our Partners & Affiliates

AIM are partners with NBS. Our products can be found on NBS Source and have been authored to NBS specification standards and have both CAWS and Uniclass 2015 classifications.

AIM are members of Centre for Window and Cladding Technology & ASFP.

AIM working in partnership with Rockwool.