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SP Firestop VRB is a product specifically designed to form open-state cavity fire stops within buildings, which allow for ventilation and drainage of the cavity under service conditions.

It has been tested with ROCKWOOL RAINSCREEN DUO-SLAB to ASFP TGD 19: “Fire resistance test for ‘Open State’ cavity barriers, used in the external fabric of buildings”. The combination of non-combustible insulation and an effective fire barrier supports fire safe façade systems and aids the design of high rise buildings above 18 m.

The product comprises of a stone wool barrier with a continuous intumescent strip to its leading edge, encapsulated by a weather-resistant polythene sleeve. Installed horizontally and designed to ensure an appropriate open air space is maintained, the SP Firestop VRB is suitable for cavity widths up to 300 mm.


  • Up to 60 minutes fire integrity and insulation.
  • Satisfies NHBC and CWCT guidance for ventilation gaps at fire barrier locations.
  • Weather resistant.
  • Easy site storage and handling.
  • Combined with Rockwool Rainscreen Duo-slab it simplifies the design of high rise buildings above 18 m.

General information
Uniclass 2015
Pr_25_80_80_42 Intumescent coated foil mesh flexible cavity barriersPrimary

F30/18 Cavity closers

F30/180 Cavity closers

K10/530 Cavity fire barriers within partitions/ wall linings

P10/420 Sleeved mineral wool small cavity barriers

P10/70 Sleeved small cavity barriers

P10/75 Wired small cavity barriers

Specification data - Intumescent coated foil mesh flexible cavity barriers
Product Reference



75 mm

125 mm

150 mm

175 mm

205 mm

225 mm

250 mm



65 mm pig tail screw

ROCKWOOL SP Firestop VRB Fixing Brackets

Standard product features


75 mm.


1000 mm.

Reaction to fire class:

A1 to BS EN 13501-1.

Product Options

Standards and approvals:

Fully tested to ASFP TGD 19: “Fire Resistance Test for ‘Open-State’ Cavity Barriers used in the external envelope or fabric of buildings”.

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