Cable trays can pass through stairwells if properly supported, firestopped, and installed to maintain safety and accessibility.

Firestopping Requirements

When cable trays pass through stairwells, which are often considered fire-rated escape routes, it is critical to maintain the integrity of fire barriers. Openings around cable trays must be sealed with fire-resistant materials such as firestop packs, firestop mastic, fire-rated boards, or mineral wool. Gaps between the firestop material and cables should not exceed 1 cm², and packing thickness should meet minimum design requirements. For large openings, a fire-resistant backing plate should be installed before sealing. Cover plates should be square, evenly painted, and fully close the opening to prevent smoke and fire spread .

Structural Support and Installation

Cable trays are mechanical support systems for cables and must not be used as walkways or ladders. Supports should provide sufficient strength to handle the weight of installed cables and any future additions. A minimum clearance of 300 mm above or between installed systems is recommended to allow for cable installation and maintenance. Electrical continuity should be maintained every 18 meters, and trays should be properly grounded . The installation should follow standards such as BS EN 61537 for cable trays and BS 6946 for channel support systems .

Safety Considerations in Stairwells

• Do not use cable trays as a walkway; stairwells are high-traffic areas, and using trays as support for people can cause injury and damage the system .
• Ensure trays are securely fastened to structural elements without cutting or drilling critical building members without approval .
• Maintain accessibility for inspection, maintenance, and future cable additions.

Fire-Rated Cable Tray Systems

For critical circuits, consider fire-rated cable trays or devices like EZ-Path, which allow cables to pass through fire-rated walls without compromising fire integrity. These systems can withstand fire for up to two hours and can be retrofitted onto existing cable trays, making them suitable for stairwell penetrations where fire safety is paramount .

Summary

Cable trays can safely pass through stairwells if:

• Firestopping is applied correctly to maintain fire-rated barriers.
• Structural supports meet load and grounding requirements.
• Trays are not used as walkways and maintain proper clearance.
• Fire-rated systems are considered for critical circuits. Following these guidelines ensures compliance with safety standards, maintains the integrity of stairwell fire barriers, and allows for safe installation and maintenance of cable systems .