Horizontal Fire Closer

A barrier that prevents the vertical passage of fire and sound in external wall cavities.


The AIM Horizontal Fire Closer is a semi rigid Rockwool stone wool insulation laminated to a polythene DPC. It has been designed to provide up to two hours resistance to the spread of fire within a cavity that is adjacent separating floors within multi story buildings. It also significantly reduces flanking sound transmission within external wall cavities.


The AIM Horizontal Fire Closer has been designed to provide up to two hours resistance to the spread of fire within a cavity that is adjacent to separating floors within multi story buildings. It also significantly reduces flanking sound transmission within external wall cavities.

The Horizontal Fire Closer is supported with test evidence to show its performance in cavity walls constructed from a variety of different substrates including masonry, timber frame structures and SFS / through wall systems.


  • A section of Rockwool Stone Wool insulation laminated to a Polythene DPC.
  • DPC Polythene conforming to BS 6515
  • Stone wool and DPC dimensions to suit most external wall cavity sizes.


  • Up to 2 hours fire resistance.
  • Prevents spread of fire past separating floors
  • Reduces flanking sound transmission within external wall cavities adjacent to separating floors
  • Test evidence that supports the use within a wider range of substrates

* For cavities in excess of 100mm, please use the AIM Wall Cavity Barrier complete with Polythene DPC



  • Thermal Conductivity: λ = 0.034W/mK
  • Complies with Part E of the Building Regulations
  • Fire resistance performance of up to 2 hours’ insulation and integrity when installed with clips
  • Rockwool stone wool insulation
  • Length: 1200mm
  • Width: 260mm – bespoke widths available upon request.
  • Thickness (mm): 50, 65, 75, 90, 100 – bespoke thicknesses available on request.
  • DPC Polythene
  • DPC Length: 1300mm
  • DPC Width: 600mm
  • DPC Overlaps: Top – 300mm, Bottom – 40mm, End – 100mm
  • The Rockwool insulation used for the Horizontal Fire Closer, is pre-compressed to enable it to take up any minor irregularities in the substrates.
  • Packaging: AIM Horizontal Fire Closers are generally packed into cartons and stretch wrapped onto wooden pallets with a showerproof polythene pallet cover and high quality edge protectors.


AIM Horizontal Fire Closer is supplied pre-cut in 1200mm lengths, 260mm wide and thicknesses depending on the fire rating required. The product supplied is as required to fill the void.

The pre-cut product is supplied with the required fixing clips



The product has been tested to BS EN 1366-4 to provide up to 120 minutes integrity and insulation.

Fire Rating (Integrity / Insulation)

- all horizontal and vertical use
Cavity width 100mm

ApplicationIntegrity / Insulation
Masonry to Masonry120/120 minutes
Masonry to Softwood60/30 minutes
Masonry to OSB60/60 minutes
Masonry to CP Board / SFS60/60 minutes


AIM Horizontal Fire Closer may be used to reduce the passage of flanking sound through external wall cavities.

It complies with Approved Document E to the Building Regulations and provides at least 23db Rw (minimum 140mm bearing). It also helps in meeting the requirements of Robust Details..


WF 432745 = Masonry
WF 399452 = Timber & SFS
WF 414885 = Timber & SFS

Z11012 – Acoustic Performance – Testing on mineral fibre insulation. To BS EN ISO 10140-2.


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


The AIM Horizontal Fire Closer should be installed in the external wall cavity at the level of the separating floor. The closer is installed with the wide DPC overlap uppermost, as indicated in the illustrations with the DPC embedded into the inner blockwork in the mortar layer above the closer, so as to form a cavity tray. When used with a sheathing board, the DPC should be dressed behind the breather membrane.

Horizontal Fire Closer are designed for use in cavities up to 100mm (for 100mm+ use WCB with DPC).

They have been tested vertically and horizontally to BS EN 1366-4.

They are installed under compression (minimum 5% compression required).

They should be installed with fixing clips

Non-standard sizes and DPC offsets are available


• PPE abrasion resistant gloves
• PPE impact resistant goggles
• RPE dust mask
• Drill
• Screwdriver
• Tape measure


Products are supplied in cartons on wooden pallets with edge protection and a shower proof hood. Orders can be supplied without cartons on request.

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 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]


We 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 are working in partnership with Rockwool.