Cable shafts and trays must be sealed with fire-resistant materials, ensuring tight, crack-free closures with proper packing, waterstops, and backing plates according to design and safety standards.

Firestopping Principles

All openings where cables, busways, or trunking pass through walls, slabs, or enter electrical panels must be tightly sealed with firestopping materials to prevent fire and smoke spread. Sealing should be reliable, without visible cracks or voids, and allow for maintenance access and proper cable routing .

Materials and Methods

• Fire-resistant materials: Use fire-rated boards, firestop packs, firestop mastic, or fire-resistant mineral wool .
• Firestop packs: Should be installed in an orderly sequence, with gaps between packs and cables not exceeding 1 cm² and a minimum packing thickness of 24 cm .
• Backing plates: For large openings, install a fire-resistant backing plate before sealing to support the firestop material .
• Cover plates: Must be square, of consistent dimensions, evenly painted, and used to close the opening .

Cable Tray and Shaft Specifics

• Slab penetrations: Provide 20–30 mm of firestopping and install a fire-support plate at the top. Cable trays and busways at floor level or slab penetrations should have a waterstop of at least 50 mm in height .
• Metal trunking: All gaps inside and around metal trunking must be sealed completely both internally and externally .
• Layout and positioning: Must facilitate installation, maintenance, and grounding, ensuring cables are properly restrained and supported .

Installation Sequence

1. Reserve openings in walls or slabs.
2. Install busways and cable trays.
3. Position and install distribution boxes.
4. Install conduits and route cables.
5. Complete grounding and waterproofing steps.
6. Apply firestopping materials according to design specifications .

Standards and Compliance

• Cable tray systems should comply with BS EN 61537 and channel support systems with BS 6946 .
• Firestopping must meet local building codes and fire safety standards, ensuring that the installation can withstand fire exposure and maintain structural integrity . By following these requirements, cable shafts and trays will be safely sealed, minimizing fire risk, maintaining electrical safety, and ensuring compliance with technical and regulatory standards.