Wall Cavity Fire Barrier

Fire and Smoke Barrier for masonry cavity walls.


AIM Wall Cavity Fire Barrier is made from foil faced high density Rockwool stone wool and is suitable for use in all masonry cavity walls, as well as for fire stopping between a curtain wall system and a concrete floor slab. The barrier prevents the passage of heat, flame and smoke within the cavity it fills for one or two hour fire rating periods.


AIM Wall Cavity Fire Barrier may be used to provide a fire barrier in masonry curtain wall systems and masonry cavity walls. 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.


  • High density foil faced stone wool barrier
  • Thicknesses to provide 1 and 2 hour fire rating
  • For use within voids up to 400mm
  • Reduces airborne transmission of sound by a minimum of 21db Rw


  • Prevents the passage of Heat, Fire and Smoke through external wall cavities.
  • Reduces airborne sound through the external wall cavity.
  • The product provides up to 120 minutes Integrity & Insulation when tested to BS 476-20



AIM Wall Cavity Fire Barrier cut to size

• Lengths: 1000mm
• Thickness: 75mm or 100mm
• Foil Facing (with AIM logo)
• Cavity widths: 50 - 400mm (barrier to be compressed by 5%)
• Faced with reinforced aluminium foil for enhanced smoke resistance

PACKAGING (cut product)

AIM Wall Cavity Fire 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
• 75mm: 60 minutes
• 100mm: 120 minutes
• Slab size: 1000 x 600mm and 1000 x 1200mm
• Foil facing imprinted with AIM logo.
• 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 Fire 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.


  • Foil tape for sealing joints where the barrier is installed in cavities over 250mm.
  • Barrier with a DPC*
  • Barrier in a polythene sleeve*

* These product variants are available but have not been fire tested. Their use would be subject to the approval of the projects fire engineer or consultant. https://www.aimlimited.co.uk/wp-admin/post.php?post=601&action=edit#



Performance is related to barrier thickness.

Tested to BS 476-20 and assessed by the Building Research Establishment (BRE).

Thickness of Fire BarrierIntegrity / Insulation
75mm - up to 400mm cavity60 minutes
100mm - up to 400mm cavity120 minutes

Joints must be taped where the cavity is over 250mm


BRE Global Assessment Report P105043 - 1004


More drawings available in the Technical Guide which can be downloaded above.


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. Installations in cavities over 250mm should also use foil tape between adjoining sections.


Clips are required when the barrier is installed. Two clips per length are required for cavities up to 400mm. Clips are supplied as flat strips, prenotched to allow them to be easily formed on site and with prestressed 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 barrier, the clips should be embedded in the barrier to approximately ¾ barrier width prior to fitting so that the top leg of the clip is level with the top of the barrier. The barrier is pushed into the cavity until the top leg of the clips touches the floor slab, and the top surface of the cavity barrier is flush with the slab.

For vertical barrier, where clips are used these may have to be fixed to the inner wall, before the barrier is installed. When the barrier has to be installed before the outer wall layer, the barrier may require retaining straps to prevent it falling off prior to completion of the wall.

Butt end joints must be tight. The ends of adjoining barriers must be fitted in contact for the full barrier width and taped in cavities over 250mm.


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)


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 safety handing information sheet is available upon request.

A Product Safety and Handling Information Sheet is available upon request.


Global warming potential = zero For product recycling please contact Rockwool T: 01656 868400 E: [email protected]


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]

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.