Cable trays placed near wall openings

Cable trays passing through wall openings must be properly firestopped, sealed, and supported to maintain safety, prevent fire spread, and comply with building codes.

Firestopping Requirements

When cable trays penetrate walls, all openings must be sealed with fire-rated materials to prevent the spread of fire and smoke. Common firestopping materials include fire-rated boards, firestop packs, firestop mastic, and fire-resistant mineral wool. For large openings, a fire-resistant backing plate should be installed before sealing, and gaps around cables should not exceed 1 cm², with packing thickness of at least 24 cm.

Cover plates should be square, evenly painted, and fully close the opening. Intumescent coatings or firestop systems, such as FIRSTO modular firestops, allow for easy installation around cable trays and provide flexibility for adding or removing cables later while maintaining fire protection. For fire-rated walls, cable trays should be coated with intumescent material on both sides of the wall to prevent heat conduction and ignition of materials on the opposite side.

Installation Guidelines

Tray alignment: Cable trays should follow the shortest and straightest path through walls, avoiding unnecessary bends or overlaps with other services. Tray type and material: Indoor trays are typically painted steel or galvanized steel, while outdoor or corrosive environments may require stainless steel, aluminum alloy, or fiberglass-reinforced trays. Sealing at wall penetrations: Use UL-listed firestop systems such as 3M pillows or moldable putty to fill gaps around trays.

The number of pillows depends on the tray size, and openings should be slightly larger than the tray to allow proper packing. Mechanical support: Ensure trays are firmly connected, straight, and properly grounded. Heavy loads should be supported to prevent deformation or failure.

Maintenance and Inspection

Regular inspection is essential to ensure firestop integrity, tray alignment, and coating effectiveness. Check for corrosion, moisture accumulation, or damage to fireproof coatings, and repair or replace materials as needed.

Summary

Properly routing cable trays through wall openings requires careful planning, firestopping, and mechanical support. Using fire-rated materials, intumescent coatings, and modular firestop systems ensures compliance with safety standards, prevents fire spread, and allows for future maintenance or cable additions.