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Siderise CT | Cavity Tray – Technical Data

Version: 1.10 - Release Date: June 2023


Siderise CT Cavity Tray has been specially developed to meet the new requirements of Approved Document B for relevant buildings, where the use of traditional combustible cavity trays is no longer permitted above 18m in steel-framed structures (SFS).
Reaction to Fire
Siderise CT has a ‘Reaction to Fire’ classification of ‘A2-s1, d0' to EN 13501-1 (Classification report available on request) and is therefore compliant for use with steel-framed structures (SFS) in relevant buildings above 18m.
Damp Proofing
As with traditional cavity trays, Siderise CT provides an essential damp proof course (DPC) that crosses the cavity of a masonry wall to direct water out of the external face of the wall and to prevent dampness from permeating the internal skin of a wall.
Siderise CT is a lightweight solution that is simple to install and provides a durable solution to the problem of damp penetration below the roofline of a masonry structure. It is easy to handle and can be installed on-site without any specialist equipment.
•  BBA Certified (21/5978)
•  Classified 'A2-s1, d0' to EN 13501-1
•  Suitable for SFS constructions above 18m
•  Fast to install, easily adjusted to suit site tolerances.
•  Flexible design to accommodate building movement.
•  Patented design
The product has a running length of 1m with a 50mm overlap joint. It is manufactured to triangular sections with a height of 150mm, an additional 50mm ‘top flange’ to the back wall and a 105mm ‘bottom flange’ at the base. The width is then manufactured to suit the cavity size. A typical cavity width accommodated for the product is between 100mm to 350mm (for other cavities please contact Technical Services). Drainage is facilitated via weep holes as normal.

Product Description

Siderise CT Cavity Tray's design features include dual aluminium skins to produce a secondary defence against moisture ingress. The aluminium faces are robust and durable to cope with site installation whilst ensuring that the water permeability is not compromised. The same unique formulation of stonewool is used in the central core as is used for all Siderise® fire barriers to maintain continuity of performance. Refer to the Installation Instructions and Standard Details for product sequencing.

Fire Performance

Reaction to Fire: Classified 'A2-s1, d0' to EN 13501-1

Thermal Performance

Thermal conductivity for Stonewool Core: λ90/90 = 0.034 W/m.K (EN 12667)

Technical Specification

Table 1 : Product Properties

Property Value 
Reaction to Fire Classification to EN 13501-1: 'A2-s1, d0' 26/11/2021, WarringtonFire (WF 432839) 
Water flow BBA Test Method, BBA (Test Report T964369) 
Shear strength EN 1052-4: 2000, BBA (Test Report T964369) 
Flexural bond strength DD 86-1 :1983, BBA (Test Report T964369) 
Heat Aging BBA Test Method, BBA (Test Report T964369) 
Adhesion to mortar BBA Test Method, BBA (Test Report T964369) 
Watertightness – joints BBA Test Method, BBA (Test Report T964369) 
Bond Strength – joints EN 12317-2: 2010, BBA (Test Report T964369) 
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 Product assembly provides suitable damp proofing in accordance with codes of practice for masonry constructions.
The stonewool core is non-hygroscopic and unaffected by humid atmosphere. 
Compatibility Protect from mortar snots during installation. 
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. See Safety Data Sheet 7.1. 

Siderise offers a number of ancillary products to complement CT, these include:

  • Siderise CT Aluminium Jointing Tape which must be used at all joints and intersections.
  • Siderise 'DPM Seal' which must be used where embedded in mortar. The DPM is pre-applied to the bottom flange of the CT, while additionally, the DPM tape is applied to the ends of the CT which are in contact with masonry reveals.
  • Siderise pre-formed Stop Ends as required; please see Table 2.

Table 2: Stop End Sizes

Void Size (mm) Stop End Length (mm) Stop End Height (mm) Stop End Return (mm) 
100 – 200 205 75 50 
201 – 350 305 75 50 

Note: The above cavity stop ends are supplied as Stainless Steel 304 Grade at a 0.5mm thickness.

Table 3: Physical Characteristics

Characteristic Value 
Manufacturer and Product Name Siderise CT- Cavity Tray 
Product Type Cavity Tray 
Code/Model/Reference/SKU CT 
Description See 'Product Description' section 
Application/Use See 'Application' section 
Material See Safety Data Sheet section 3.1 
Weight 0.79-2.75Kg as per 100-350mm wide voids 
Finish /Colour Grey with silver shades aluminium wrapped faces with black taped lower lip. Solid, green-brown on exposed side faces. 
Packaging Packaged in cartons 
Pack Size Carton Size: Length-1070mm, Width-600mm, Depth-400mm(maximum) 
Unit of measure millimetre (mm) 
Chemical properties/Safety data sheets See Safety Data Sheet section 3.1 
Size/dimensions (product & installation spatial requirement) Length of 1m with a 50mm overlap joint, manufactured to 150mm height triangular sections, an additional 50mm ‘top flange’ to the back wall and a 105mm ‘bottom flange’ at the base. Typical cavity width between 100mm - 350mm covered. 
Shelf life 12 Months; Store in dry conditions and protect from mechanical damage. 


  • Zero Ozone Depleting Potential
  • Zero Global Warming Potential
  • Recyclable.Siderise CT is composed predominantly of stonewool and soft tempered aluminium, both of which are suitable for recycling.

Additional Information

The following information is available for download via the website:

  • Safety Data Sheet
  • Product Brochure
  • Standard Details
  • Installation Instructions
  • Installation Video
  • NBS Specification Clauses

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: CT_v1_10_20230623_1538