AIM Cavity Fire Closers

AIM semi-rigid Rockwool stone wool to polythene DPC Cavity Closers. The AIM Cavity Closer system has been designed to close masonry cavities for fire, thermal and acoustic purposes; it reduces cold bridging when closing cavities at door and window frames.Rockwool red logo      

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  • Thermal Conductivity: λ = 0.034W/mK
  • Ozone depletion potential of zero. No CFCs or HCFCs used in manufacture
  • Global warming potential = zero

Rockwool stone wool insulation

  • Length: 1200mm
  • Width: 100, 150, 190mm
  • Thickness: 20, 50, 65, 75, 100mm

DPC Polythene

  • Length: 1300mm
  • Side overlap: 40mm
  • End overlap: 100mm

Fire Performance

The performance of the AIM fire protection range has been tested to BS 476 part 20 and assessed by Warrington Fire Research Centre. The AIM Cavity Closer will provide a fire rating of up to 4 hours, please refer to the fire data for AIM Fire Stop Strip. AIM mineral wool products are non combustible to BS 476 part 4, rated Class 1 Surface Spread of Flame to BS 476 part 7 and comply with the performance requirements of Class O of the Building Regulations (does not apply to the DPC).

The DPC conforms to BS 6515 (1984).


AIM Cavity Closer may be used to prevent the passage of flanking sound within masonry cavities. It complies with Approved Document E 2003 to the Building Regulations. Helps in achieving requirements of Robust Details.


The AIM Cavity Closer system has been designed to close masonry cavities for fire, thermal and acoustic purposes; it reduces cold bridging when closing cavities at door and window frames. The AIM Cavity Closer will accommodate movement in the building and allow for any irregularities in the cavity.

The AIM Cavity Closer should be fitted with the DPC against the inside face of the outer wall, one 40mm DPC overlap extending into the cavity, and the other overlap protruding from the cavity. This protruding lap should be folded against the side of the outer brickwork behind the window or door frame.

Where more than one AIM Cavity Closer is required, the Closers should be fitted with 100mm DPC overlap at the base. The next Closer should be installed to give a tight butt joint of the mineral wool insulation. The top of vertical cavity closers should be by a cavity tray or sealed to the underside of the lintel.

Non standard sizes and DPC offsets are available.

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