Party Wall Fire Closers

Prevents the passage of fire, smoke and sound in all three directions at the party wall junction.


AIM Party Wall Fire Closers are semi-rigid Rockwool stone wool laminated to a polythene DPC. They have been designed to provide at least one hour resistance to the spread of fire and smoke in all three directions at the party wall junction. It also significantly reduces flanking sound transmission within external wall cavities.


The Party Wall Fire Closer is supported with test evidence to show its performance in cavity walls constructed from a variety of different substrates including masonry, many 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 cavity wall / party wall junctions.


  • Closes cavities up to 100mm thick*
  • Up to 2 hours fire resistance in all three direction
  • Closes masonry cavities for fire, thermal and acoustic purposes.
  • Now with 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 to either side of the party wall junction.




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

Fire Rating (Integrity / Insulation)

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 Party Wall 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 14 dB RW (75mm bearing) 18dB RW (100mm bearing) 23 dB RW (140mm bearing). It also helps in achieving requirements of Robust Details.

ApplicationIntegrity / Insulation
Masonry to Masonry120/60 minutes
Masonry to Softwood30/30 minutes
Masonry to OSB30/30 minutes
Masonry to CP Board / SFS30/30 minutes

Cavity width of 100mm - 100mm bearing on the party wall.


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.


• Thermal Conductivity: λ = 0.034W/mK
• 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 conforming to BS 6515
• DPC Length: 1300mm
• DPC Side Overlap: 40mm (non-standard DPC
offsets and widths available).
• DPC End Overlap: 100mm


AIM Party Wall 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.


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


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


The AIM Party Wall Fire Closer should be installed in the external cavity wall with an equal overlap to either side of the party wall cavity. For 1 hour fire rating in masonry cavities, the bearing on either side of the party wall must be at least 75mm.

The Fire Closer should be fitted with the DPC overlap at the bottom. At the top of the Party Wall Fire Closers, the DPC should be extended to the inner leaf of the wall to form a cavity tray or sealed to the underside of the lintel.

Approved Document B, states, “A cavity barrier should, wherever possible, be tightly fitted to a rigid construction and mechanically fixed into position” (Clause 5.22 Volume 1: Dwellings and clause 9.14 Volume 2: Buildings other than dwellings).

If required, the Party Wall Fire Closer can be supplied with fixing clips.

It is good practice to have intumescent mastic available to seal any gaps or voids local to the fire barrier.

They have been tested to BS EN 1366-4.

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

Non standard sizes and DPC offsets are available.

Party Wall Fire Closers are for use in cavities up to 100mm (for 100mm+ use the AIM Wall Cavity Barrier with a DPC to either side of the party wall junction).


• PPE abrasion resistant gloves
• PPE impact resistant goggles
• RPE dust mask
• 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]

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.