How to seal up cable tray shafts

Cable tray shafts can be effectively sealed using firestop packs, fire-resistant boards, mineral wool, and firestop mastic to ensure safety, prevent fire spread, and maintain environmental integrity.

Firestopping Techniques

When cable trays pass through walls, floors, or shafts, firestopping is essential to prevent the spread of fire and smoke. Openings should be tightly sealed without visible cracks or voids. For large openings, a fire-resistant backing plate can be installed before sealing to provide structural support and ensure complete coverage.

Common firestopping materials include: Firestop packs: These are placed around cables in an orderly sequence, ensuring gaps between packs and cables do not exceed 1 cm², with a minimum packing thickness of 24 cm. Fire-resistant boards: Used to cover larger openings or as a base for other sealing materials. Firestop mastic: Applied to fill small gaps and ensure a continuous seal around cables and tray edges.

Mineral wool: Fire-resistant mineral wool can be packed around cables and trays to provide thermal insulation and fire protection.

Installation Best Practices

Ensure floor and wall finishes in the electrical shaft are completed before sealing. Maintain reasonable layout and positioning to facilitate installation and future maintenance. Seal all gaps inside and around metal trunking completely, both internally and externally.

Use cover plates that are square, consistent in size, and painted evenly to close the opening. Follow standards such as BS EN 61537 for cable tray systems to ensure compatibility and safety.

Additional Considerations

For ventilated or solid-bottom trays, sealing should not obstruct airflow if ventilation is required for heat dissipation. Materials should be selected based on environmental conditions, including exposure to moisture, temperature variations, and potential chemical exposure. Proper sealing also contributes to mechanical protection, preventing debris ingress and maintaining cable integrity.

By combining these methods—firestop packs, mineral wool, mastic, and backing plates—cable tray shafts can be sealed effectively to meet safety, fire, and environmental requirements while allowing for maintenance access.