How to cover a firewall with cable trays

Cable trays passing through fire-rated walls must be properly firestopped using approved materials and methods to maintain the wall's fire-resistance rating.

Planning and Preparation

Before installation, ensure that the firewall and floor finishes are complete and that the electrical shaft or wall opening is properly sized for the cable tray and firestop system. Openings should be reserved and measured accurately, allowing for the thickness of firestop materials and any backing plates if needed. The layout should facilitate both installation and future maintenance.

Firestop Materials

Common firestop materials for cable tray penetrations include: Firestop boards or fire-rated boards for large openings Firestop packs or mineral wool to fill gaps around cables Intumescent caulks such as IC 15WB or HILTI FS-ONE MAX for sealing edges and gaps Moldable putty pillows for smaller gaps or irregular openings The choice of material depends on the size of the opening, the type of wall (concrete, gypsum), and the required fire rating.

Installation Steps

Install the cable tray through the wall or slab opening, ensuring it is properly supported and aligned. Insert fire-resistant backing plates for large openings to provide a stable base for firestop materials. Pack firestop materials around the cables and tray.

Gaps should be minimal, typically not exceeding 1 cm², and packing thickness should meet manufacturer specifications. Seal edges and surfaces with intumescent caulk or putty to ensure a continuous barrier against fire and smoke. Cover the top and bottom of the cable tray if required, using fire-rated covers or plates to maintain the fire-resistance rating.

Label and document the installation for compliance and future maintenance.

Compliance and Testing

Ensure that the firestop system maintains the fire-resistance rating of the wall, typically 2–3 hours for substations or critical installations. Follow manufacturer instructions for each firestop product, as improper installation can compromise fire protection. For large or complex penetrations, consider obtaining an Engineering Judgment from the manufacturer to confirm the system meets fire-rating requirements.

Best Practices

Use new, undamaged materials and ensure they are traceable from manufacturer to installation. Maintain orderly placement of firestop packs and caulks to avoid voids or gaps. Ensure cable bundles are balanced and properly banded to prevent movement that could compromise the firestop.

By following these steps and using approved firestop materials, you can safely cover a firewall with cable trays while maintaining the required fire-resistance rating and compliance with international standards.