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Double Layer Cavity Barrier

Suspended Ceilings IconDouble layer cavity barriers provide an enhanced solution where longer periods of resistance to fire and smoke are required

Double Layer Cavity Barrier

One Cavity Barrier bolted to soffit
two Metal angle
Three Two curtains of Rocksilk Smoke and Fire Barrier
Four 50mm Cavity
Five Rocksilk Smoke and Fire Barrier fixed to timber spacer

Products

Rocksilk Smoke and Fire Barrier is made from rock mineral wool, and formed into a flexible mattress faced on one side with galvanised wire mesh stitched in position. Rocksilk Smoke and Fire Barrier is also available foil faced on one or both sides.
 

Typical Construction

For one hour fire resistance. Two layers of 50mm Rocksilk Smoke and Fire Barrier, separated by a 50mm air space, applied as a hanging curtain with wire mesh to the outside, supported continuously from above and both sides.
 
At the base it is either lapped freely on to the back of a suspended ceiling, or fixed to a partition head. Use foil faced Rocksilk Smoke and Fire Barrier when the ceiling void is used as an air plenum.
 

Installation

Click here for installation details.
 

Performance

Fire performance

 
The base rock mineral wool of Rocksilk Smoke and Fire Barrier is classified as non-combustible to BS 476: Part 4: 1970. Rocksilk Smoke and Fire Barrier has a Class 1 surface spread of flame to BS 476: Part 7: 1997 and is Class ‘O’ to the Building Regulations.
 
When subjected to full-scale fire resistance tests to BS 476: Part 22: 1987, a system comprising a double layer of 50mm Rocksilk Smoke and Fire Barrier, fixed as specified on page 7, achieved 61 minutes insulation, and retained its integrity for 66 minutes, after which time the test was discontinued.
 
A double layer of 50mm Rocksilk Smoke and Fire Barrier thereby satisfies the criteria laid down in the Building Regulations for one hour cavity barriers. These tests incorporated vertical and horizontal joints between barriers. Fire resistance is effective from either side of the barrier.
 
When tested, the wire side was exposed to the furnace. This is the side most vulnerable to fire. Tests are available for a two hour fire test. Apply directly to Knauf Insulation for details.
 

Acoustic performance


A cavity barrier, comprising a double layer of foil faced 50mm Rocksilk Smoke and Fire Barrier, fixed as shown on page 6, will offer significant sound reduction. When coupled with a ceiling system offering at least 32 dB sound reduction and fixed to the head of the partition, the flanking path through the ceiling and cavity barrier can achieve a sound reduction of 50 dB.
 

Advantages

  • Two Layers of 50mm Rocksilk Smoke and Fire Barrier with 50mm airspace
  • Wire mesh to the outside
  • System uses standard metal components
  • Achieves 1 hour fire protection in terms of both insulation and integrity System offers both fire and acoustic performance

  Installation Instructions

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