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Siderise EW – Cavity Barriers and Fire Stops for Masonry External Walls – Technical Data

Version: 1.41 - Release Date: October 2021


Siderise EW Systems have been developed to provide a simple and easy to install method of sealing external wall cavities for fire and smoke in external masonry constructions.

  • EW-CB30 is for use as a Cavity Barrier in accordance with building regulations.
  • EW-FS120 is for use as a Fire Stop in accordance with building regulations.

Additionally, the products have excellent sound reduction qualities which can be used to combat unwanted noise via flanking transmission.

These products represent an ideal combination of fully qualified performance and practical installation.

Siderise EW has 'Certifire' 3rd party approval (CF 5727).

Product Description

Siderise EW Systems comprise of a low resin content stone wool insulation core which is pre-compressed internally to form a resilient strip. The material is faced on two sides with a reinforced Class 0 aluminium foil which is an effective smoke barrier. Available in the following forms:

Pre-cut Strips

  • Pre-cut products are available in 1mm increments of width to suit the cavity size. Please see Table 1 regarding 'fit type'.
  • Supplied with appropriate brackets as part of a system.


  • Standard sheet size is 1200 x 1200mm and may be of benefit when the actual void size is not known or where it varies significantly.
  • Appropriate brackets must be ordered separately.

Siderise EW should be installed in accordance with PD6697:2019 - 'Recommendations for the design of masonry structures to BS EN 1996-1-1 and BS EN 1996-2'.

  • Horizontal - EW must be installed with a suitable cavity tray immediately above.
  • Vertical - EW must be installed with a DPC extending a minimum of 25mm into the cavity either side. DPC to be sourced separately.

Fire Performance

Siderise EW Systems have been tested in conjunction with a DPC in accordance with EN1366-4:2006 + A1:2010.

  • Resistance to Fire - the 'EI' classification, is expressed as the minimum value in minutes of both the Integrity (E) and Insulation (I) performance, as defined in EN 13501-2. Please see Table 1.
  • Reaction to Fire - 'A1' classification to EN13501-1.

Siderise EW Systems have 'Certifire' 3rd Party Approval - certificate CF 5727 refers. 

Table 1 : Resistance to Fire to EN1366-4

Orientation EW System Thickness Gap Width (mm) Fit Type Brackets (G/S) Classification (minutes) Certification 
Vertical EW-CB30 75mm 20-50 +10% Compression n/a EI 30 (Applied for) 
     51-150 Friction B65/110 EI 30 CF 5727 
     151-250 Friction B195 EI 30 CF 5727 
     251-350 Friction B355 EI 30 (Applied for) 
     351-450 +10mm Compression B355 EI 30 CF 5727 
 EW-FS120 120mm 20-50 Friction n/a EI 120 (Applied for) 
     51-150 Friction B65/110 EI 120 CF 5727 
     151-250 Friction B195 EI 120 CF 5727 
     251-350 Friction B355 EI 120 (Applied for) 
     351-450 +10mm Compression B355 EI 120 CF 5727 
Horizontal EW-CB30 75mm 20-50 +10% Compression n/a EI 30 (Applied for) 
     51-150 Friction B65/110 EI 30 CF 5727 
     151-250 Friction B195 EI 30 CF 5727 
     251-350 Friction B355 EI 30 (Applied for) 
 EW-FS120 120mm 20-50 Friction n/a EI 120 (Applied for) 
     51-150 Friction B65/110 EI 120 CF 5727 
     151-250 Friction B195 EI 120 CF 5727 
     251-350 Friction B355 EI 120 (Applied for) 

  • All brackets to be suitably fixed to substrate with non-combustible fixings, or mortared into masonry coursing.
  • All brackets to penetrate product at mid-thickness.
  • All brackets to penetrate to a depth of 75% of gap width.
  • Brackets are available in two forms: (G) denotes galvanised steel brackets and (S) denotes stainless steel brackets.
  • Brackets must be installed at 600mm centres based on a 1200mm strip. This can be reduced pro rata for shorter lengths. Please note that 2 brackets are required for any length of barrier greater than 300mm. For lengths ≤300mm a single bracket must be utilised.

Friction Fit - product should be sized equal to the void width and installed with no gaps.

Please note product supplied in strip form will have a -0mm/+4mm tolerance.

Compression Fit - the product should be sized to the void width plus a minimum of +10mm or 10% compression (Please see Table 1).

Please see separate installation instructions (available for download from our website) for more information.

Siderise EW has been tested in accordance with the stated test standard for masonry assemblies. The stated classifications (EI) have in some instances been stated lower than achieved in testing, this is to keep simplicity in the range as either a 30-minute or 120-minute product. For specific Integrity (E) and Insulation (I) values please refer to Certifire CF 5727.

When considering Steel Frame Systems (SFS) it is imperative that the supporting structure is of at least an equal fire performance rating to that of the Cavity Barrier or Fire Stop.

For other void sizes or additional advice, please contact Technical Support.

Acoustic Performance

Siderise EW additionally provides an effective sound barrier as the material construction and inherent properties of the stonewool core afford the EW exceptional acoustic performance.

Their acoustic performance is attributable to the mass of the stonewool core coupled to the unique resilient lamella board internal construction. Also, the foil facings and the additional sealing of joints with foil tape all serve to provide improved air tightness.

Based on laboratory tests to determine airborne sound transmission in accordance with BS EN ISO 140-3: 1995, the following Weighted Sound Reduction Index (Rw) values can be used.

Table 2 : Weighted Sound Reduction Index

EW System Thickness (mm) Rw (dB) 
EW-CB30 75 21 
EW-FS120 120 25 

Sound Research Laboratories Ltd. Test report no.  C/99/5L/7743 refers.

When properly installed at external masonry cavity wall junctions, the EW Systems will significantly reduce any potential flanking transmission. The precise value will depend upon the specifics of the construction.

Please contact Technical Support for project-specific advice.

Thermal Performance

Thermal conductivity : λ10 = 0.038 W/m.K (tested foil to foil)

Damp Proofing

Siderise EW must be damp-proofed in accordance with PD6697:2019 - 'Recommendations for the design of masonry structures to BS EN 1996-1-1 and BS EN 1996-2'. 

Technical Specification

Siderise EW - Cavity Barriers and Fire Stops

Table 3 : Product Properties

Property Value 
Reaction to Fire Classification to EN 13501-1 : 'A1' 
Resistance to Fire Classification to EN 13501-2 : Please see Table 1 
Thermal Conductivity λ10 = 0.038 W/m.K (tested foil to foil) 
Chemical The base stone wool is chemically inert. An aqueous extract of the rock wool is neutral (pH7) or slightly alkaline. Resistant to most acids and weak alkaline solutions. 
Biological Vermin and rot proof and does not encourage the growth of fungi, moulds or bacteria. 
Effect of water Non-hygroscopic. Unaffected by humid atmosphere. Must be suitably damp proofed in accordance with codes of practice for masonry constructions. 
Compatibility Compatible with all normal building materials. 
Maintenance No maintenance required unless disturbed. 
Handling Easy to handle but should be treated with due care to ensure material integrity and shape are maintained. 
Storage Store in dry conditions. 

Siderise offers a range of ancillary products to complement the EW range these include:

Fixing Brackets must be used in the installation of the product:

  • B65/110 (51-150mm voids)
  • B195 (151-250mm voids)
  • B355 (251-450mm voids)

Brackets come in two forms: 'G' - Galvanised Steel Brackets and 'S' - Stainless Steel Brackets.

Brackets are supplied with all EW in strip form, but must be ordered separately for all EW in sheet form.

Aluminium Jointing Tape must be used at all joints and intersections:

  • RFT120/45 (120mm wide x 45m rolls)
  • Adhesive backed
  • Supplied in boxes of 8

Fire & Acoustic Sealant may be used for small gaps and undulations:

  • FS120/310ML/WH (310ml cartridge)
  • Supplied in boxes of 25


Siderise EW Systems are environmentally friendly:

  • They contain no Volatile Organic Compounds (VOCs) and no very Volatile Organic Compounds (vVOCs).
  • Zero Ozone Depleting Potential
  • Zero Global Warming Potential
  • Recyclable

Additional Information

The following information is available for download via the website:

  • 3rd Party Certificate - CF 5727
  • Standard Details
  • NBS Specification Clauses
  • Installation Instructions
  • Safety Data Sheet

Technical Support

For technical advice or support please contact:

For Installation Training or Site Inspections please contact:


The information in this datasheet is believed to be accurate at the date of publication. Siderise has a policy of continuous product improvement and reserves the right to alter or amend the specifications of products without prior notice. Siderise does not accept responsibility for the consequences of using the products described outside of the recommendations within this datasheet. Expert advice should be sought where there is any doubt about the correct specification or installation of Siderise products.

Published Version: EW_v1_41_20211117_175