Product description

An advanced intumescent strip fixed to high density non-combustible ROCKWOOL insulation, SP Firestop OSCB is designed to form an open-state cavity barrier within a rainscreen system. This allows ventilation and drainage under normal service conditions, while in the event of a fire the intumescent strip quickly expands outwards to seal the cavity, preventing the passage of fire and smoke.


Designed for use only in conjunction with ROCKWOOL RAINSCREEN DUO SLAB, SP Firestop OSCB forms an open-state cavity fire barrier within a rainscreen cavity.


The product is available in two variants giving up to 60 and 120 minutes’ fire performance respectively: SP Firestop OSCB 60 and SP Firestop OSCB 120.


Each comprises of a continuous intumescent strip fixed to the leading edge of a foil faced stone wool barrier, encapsulated by a weather-resistant polythene sleeve – coloured white for OSCB 60 and red for OSCB 120.


Fully tested to ASFP TGD 19, the combination of non-combustible insulation with an effective intumescent supports the construction of safe façade systems and aids the design of high-rise buildings over 18m in height.


Installed horizontally and designed to ensure an appropriate open air space is maintained, SP Firestop OSCB is suitable for cavity widths up to 425mm.


  • Fully tested to “ASFP Technical Guidance Document 19: Fire resistance Test for ‘open-state’ cavity barriers used in the external envelope or fabric of buildings”
  • Up to 120 minutes fire integrity and insulation
  • Provides 25mm or 44mm airspace
  • Satisfies NHBC and CWCT guidance for ventilation gaps at fire barrier locations
  • Weather resistant
  • Easy site storage and handling
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