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Cable trays passing through walls require fireproof sealing

Fiber and communications infrastructure knowledge brief Published 09 Mar 2022

Prepared for preliminary research by the ENSAA knowledge desk. Confirm optical interfaces, port or core capacity, electrical input and output, enclosure protection, thermal design and installation limits against current standards and product documentation.

Yes, cable trays passing through walls must be sealed with fireproof materials to maintain fire-resistance integrity and prevent the spread of fire, smoke, and toxic gases.

Firestopping Requirements

When cable trays penetrate walls, floors, or slabs, the openings must be tightly sealed using fire-rated penetration sealing materials such as firestop packs, firestop mastic, fire-resistant mineral wool, or fire-rated boards. The sealing must be complete, reliable, and free of visible cracks or voids to ensure the fire barrier remains effective. For large openings, a fire-resistant backing plate should be installed before sealing.

Installation Guidelines

Gap and packing limits: The gap between firestop packs and cables should not exceed 1 cm², and packing thickness should be at least 24 cm. Cover plates: Use square, evenly painted cover plates to close the opening and maintain fire integrity. Tray types: Only fireproof trays should be used for flame containment or isolation, and the tray coating or structure must not be damaged during installation.

Waterstop and support: At slab penetrations, provide 20–30 mm of firestopping and install a fire-support plate at the top; floor-level trays should have a waterstop of at least 50 mm.

Standards and Compliance

Cable penetration seals are tested according to EN 1366-3 and classified under EN 13501-2 in Europe. Firestop systems must match the tested cable group and configuration; not all products are suitable for every cable type. In the U.

S., UL-listed systems, such as 3M fire barrier pillows or intumescent caulks, are commonly used to achieve rated fire protection for concrete or gypsum walls.

Inspection and Maintenance

Regular inspection is essential to ensure long-term effectiveness. Check for corrosion, deformation, or damage to trays and seals, and confirm that tray connections are firm and properly aligned. Any compromised firestop arrangements must be reinstated using the same type of materials as originally installed.

Practical Considerations

Maintain adequate clearance between cables to prevent heat accumulation and allow airflow. Firestopping should be integrated into the design and installation sequence, including reserved openings, tray installation, cable routing, and grounding. Temporary sealing may be used during construction but must be replaced with permanent fireproof materials before project completion.

By following these guidelines, cable tray penetrations through walls can maintain the fire-resistance rating of the building element, preventing the spread of fire and smoke while complying with regulatory standards.

Cable trays passing through walls require fireproof sealing - ENSAA OPTICAL NETWORKS [PDF]

Cable trays passing through walls require fireproof sealing

Firestopping Requirements for Cable Trays and Wall/Slab Penetrations

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Related Video Reference

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Technical note

This reference is intended for preliminary fiber and communications infrastructure research. Optical interface, fiber type, port or core capacity, electrical input and output, enclosure protection, cooling, installation limits and applicable standards must be verified for the specific project.

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