Siderise CT Cavity Tray

Factory-engineered, pre-formed and ready-to-fit cavity tray solution

Moisture management 

CT Cavity Tray is a BBA certified solution for directing penetrating moisture towards the outer skin of traditional cavity walls and steel-framed backed external masonry walls. It combines a flexible aluminium tray with a non-combustible stone wool insulation core and achieves an A2-s1,d0 reaction to fire classification under EN 13501-1. This meets the requirements of Regulation 7(2) as outlined in Approved Document B (England and Wales) for high-rise residential and other ‘relevant’ buildings. 

Holistically tested

CT Cavity Tray has been tested as a whole product to EN 13101-1 rather than relying on the performance of its component parts. This offers both peace of mind and evidence that the product as installed is fully compliant with regulatory requirements

Quick to install

Contributes to project schedule efficiencies, yielding significant advantages in build program speed and sequencing— especially on larger projects with multiple floors and where different contractors need to share mast usage

Easy to install

Requires just a cutting knife and sealing tape for joints, and details at external corners or window reveals. There is no need for costly made-to-order prefabricated corner sections, sealants and soldering, or specialist labourers, equipment, vast site storage facilities and isolated workshop zones

BBA tested and certified

BBA testing and certification included assessing joint water tightness, mortar adhesion, material durability and practicability of installation - providing reassurance that it is fit for purpose. See BBA certificate for more details

NHBC, LABC and Premier Guarantee compliance

CT Cavity Tray can comply with the requirements of major industry standard building warranty providers

Registered on BSI Identify database

Product identifier QR codes that are linked to BSI UPINS are printed on the product to allow rapid access to specification, testing, installation, and maintenance information using the BSI Identify digital identification service

External masonry wall cavity barrier and firestop systems

Closed state fire protection solutions for masonry constructions 

Learn more

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 with product made available in 5mm increments. 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 stone wool 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 stone wool core: λ90/90 = 0.034 W/m.K (EN 12667) 

Technical Specification

Table 1 : Product Properties

Table 1 : Product Properties

Properties 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
201 - 350

Table 3: Physical Characteristics

Properties 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 available in 5mm increments.
Shelf Life 12 Months; Store in dry conditions and protect from mechanical damage.

Siderise CT is composed predominantly of stone wool and soft tempered aluminium, both of which are suitable for recycling.

Additional Information Available

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.


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View our installation video

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Single source supply components for compatibility, performance and confidence

Siderise CT Cavity Tray Stop End
Siderise CT Cavity Tray Aluminium Foil Jointing Tape
Siderise CT Cavity Tray DPM Seal

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Get quick answers to common queries or contact our team for more advice. Your questions answered.

Do you offer product installation training?

Yes, our site services engineers combine classroom learning with toolbox training and includes mock-up benchmark installations, free-of-charge.

What sizes of CT Cavity Tray are available?

CT Cavity Tray is triangular, with a height of 150mm, an additional 50mm ‘top flange’ to the back wall and a 105mm ‘bottom flange’ at the base. It has a running length of 1m with a 50mm overlap joint. The width is then manufactured to suit the cavity size with product made available in 5mm increments. The width as standard is 100-350mm

Why is the fire performance of cavity trays important?

Whilst cavity trays do not function as firestops, it is vital that they do not contribute to the growth of a fire if it enters the wall cavity. With a Euroclass A2-s1,d0 reaction to fire rating, it satisfies the compliance requirements of Regulation 7(2) for ‘relevant’ buildings in England and Wales with a masonry external leaf and non-blockwork / concrete inner leaf such as SFS

What do I need to install CT Cavity Tray?

A cutting knife and sealing tape. You do not need any heavy or specialist tools, which makes the installation process very simple for setting external internal corner returns

Do I need to order corner sections?

CT Cavity Tray does not require prefabricated corner sections Instead, the product can easily be cut, installed, and sealed with our CT Aluminium Jointing Tape. See our installation instructions for more detail. 

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