Yes, cable trays that pass through walls, floors, or fire-rated barriers generally require fireproof putty or other firestopping materials to maintain fire safety and compliance.

Firestopping Requirements

When cable trays penetrate walls, slabs, or electrical shafts, the openings must be sealed with fire-rated materials to prevent the spread of fire and smoke. This is especially critical in commercial, industrial, or high-occupancy buildings where electrical systems are essential for safety and operations . Firestopping ensures that the integrity of fire-rated barriers is maintained even when penetrated by cables or trays.

Use of Fireproof Putty

Fireproof putty, such as 3M Fire Barrier Moldable Putty+, is commonly used to seal cable tray penetrations. Typically, two sticks of moldable putty are applied per opening, often in combination with firestop pillows or mineral wool, depending on the size of the tray and the wall or floor construction . The putty is pliable, adheres well to surfaces, and can conform to irregular gaps around cables, providing a reliable fire barrier.

Installation Guidelines

• Ensure the opening around the cable tray is clean and free of debris.
• For large openings, install a fire-resistant backing plate before applying putty or pillows .
• Maintain a tight seal without visible cracks or voids; gaps should generally not exceed 1 cm² .
• Fireproof putty can be used in new construction or retrofits, and it is compatible with various wall types, including concrete and gypsum .
• Additional firestop measures, such as waterstops at slab penetrations, may be required for floor-level trays .

Alternative or Complementary Firestopping

Other fire-rated materials, such as firestop mastic, mineral wool, or fire-rated boards, can also be used depending on the system design and UL-listed firestop assemblies . The choice of material should comply with local building codes and UL or FM-approved systems.

Maintenance and Inspection

Regular inspection of fireproofed cable trays is essential to ensure the putty and other firestopping materials remain intact, especially in outdoor or high-humidity environments. Any signs of cracking, corrosion, or degradation should be addressed promptly to maintain fire protection . In summary, fireproof putty is a recommended and often required component for firestopping cable tray penetrations, ensuring compliance with fire safety standards and protecting both infrastructure and human life.