Cable trays passing through structural walls

Cable trays passing through structural walls must be properly supported, sealed, and firestopped to maintain both structural integrity and fire safety.

Mechanical Support and Installation

Cable trays, ladders, or mesh trays are designed to support cables but not as enclosures or walkways. When passing through walls, they must be mounted using support elements such as wall brackets, suspended supports, or center suspensions to ensure stability and prevent sagging or stress on the cables. Fittings like horizontal or vertical bends, T-pieces, crossovers, and end closures allow the tray to change direction or dimension while maintaining proper cable routing.

The installation should follow standards such as BS EN 61537 for cable trays and BS 6946 for channel support systems.

Firestopping Requirements

When cable trays penetrate walls, firestopping is essential to prevent the spread of fire, smoke, and toxic gases. Openings around the trays must be sealed with fire-rated materials such as firestop packs, firestop mastic, fire-resistant mineral wool, or fire-rated boards. Key considerations include: Gap limits: The area between firestop packs and cables should not exceed 1 cm², and packing thickness should be at least 24 cm.

Backing plates: For large openings, install a fire-resistant backing plate before sealing. Waterstops: At slab penetrations, a waterstop of at least 50 mm is recommended, with 20–30 mm of firestopping and a fire-support plate at the top. Integrity: Seals must be tight, reliable, and free of cracks or voids, maintaining the fire-resistance rating of the wall.

Accessories: Intumescent gaskets, grommets, or fire sealants should be used for cable entries in equipment or cavity walls to preserve fire integrity.

Compliance and Best Practices

Ensure that the installation does not compromise structural stability or fire separation between building areas. Use tested and certified penetration seal systems according to standards like EN 1366-3 and classify them per EN 13501-2. Avoid mixing different firestop systems unless verified by manufacturer data, as this may compromise fire integrity.

Maintain accessibility for inspection and maintenance, and ensure layout facilitates cable routing without excessive bending or stress. By following these guidelines, cable trays can safely pass through structural walls while maintaining both mechanical support and fire safety compliance. Proper planning, material selection, and adherence to standards are critical for long-term safety and regulatory compliance.