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Siderise CT | Cavity Tray – Technical Data

Version: 1.06 - Release Date: February 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).

Siderise 'CT' is classified '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.

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
  • Accommodates building movement
  • Patented design

The product has a running length of 1m with a 50mm overlap joint, it is manufactured to 150mm triangular sections with an additional 50mm ‘flange’ to the back wall. 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.

Fire Performance

Classified 'A2-s1, d0' to EN 13501-1

Thermal Performance

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

Technical Specification

Siderise CT

Table 1 : Product Properties

Property Value 
Reaction to Fire Classification to EN 13501-1: 'A2-s1, d0' 26/11/2021, Warrington 
Water flow BBA Test Method (Test Report T964369) 14/04/2021, Watford – Pass 
Shear strength EN 1052-4 : 2000, 28/05/2021 Lucideon, Stoke-on-Trent – Pass 
Flexural bond strength DD 86-1 :1983, 20/05/2021 Lucideon, Stoke-on-Trent - Pass 
Heat Aging BBA Test Method (Test Report T964369) 16/06/2021, Watford – Pass 
Adhesion to mortar BBA Test Method (Test Report T964369) 16/06/2021, Watford – Pass 
Watertightness – joints BBA Test Method (Test Report T964369) 16/06/2021, Watford – Pass 
Bond Strength – joints EN 12317-2 : 2010 16/06/2021, BBA, Watford – Pass 
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. 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.
  • Siderise pre-formed Stop Ends as required; please see Table 2.

Table 2: Stop End Sizes

Void Size (mm) Stop End Length(mm) 
100 – 200 205 
201 – 350 305 

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, 50mm overlap joint, manufactured to 150mm triangular sections with an additional 50mm ‘flange’ to the back wall. Typical cavity width between 100mm - 350mm covered. 
Shelf life 12 Months; Store in dry conditions and protect from mechanical damage. 


Siderise CT is environmentally friendly:

  • It contains no Volatile Organic Compounds (VOCs) and no very Volatile Organic Compounds (vVOCs).
  • 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:

  • Standard Details
  • 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: CT_v1_06 _20230213_1252