Spacing requirements for cable tray ladder supports

Ladder-type cable trays should generally be supported every 4 to 6 feet, with rungs spaced no more than 9 inches apart, according to NEC and industry best practices.

Support Spacing Guidelines

For horizontal runs, the National Electrical Code (NEC) specifies that ladder-type cable trays must be supported at intervals not exceeding 5 feet, though the ideal spacing is 4 to 6 feet to ensure uniform load distribution and prevent sagging or overloading of the tray . Supports must be designed to carry the weight of the cables, the tray itself, and any additional loads such as wind, seismic forces, or maintenance activities .

Rung Spacing

The rungs of ladder trays provide direct support for cables. NEC guidelines recommend that rungs be no more than 9 inches apart for standard installations . For small-diameter control or instrumentation cables, closer rung spacing of 6 to 12 inches may be used to prevent cable drooping, while larger power cables can use 9 inches or wider spacing . Wider rung spacing and wider tray widths reduce overall tray strength, so manufacturer specifications should always be consulted .

Load Considerations

Support spacing should account for the type and weight of cables, as well as potential future additions. Light cable loads may allow for maximum spacing, but heavily loaded trays require closer supports to maintain structural integrity . Always verify that the tray and support system meet deflection limits and manufacturer load ratings .

Installation Best Practices

• Secure trays to building structures using appropriate brackets, hangers, or channel supports .
• Ensure supports are level and evenly spaced to avoid uneven stress on the tray and cables .
• Avoid cutting or drilling structural members without approval .
• Consult the tray manufacturer for guidance on modifications or field adjustments, especially if rung spacing needs to be altered for cable bending radii . By following these guidelines, ladder-type cable trays can provide safe, durable, and code-compliant support for electrical and communication cables in commercial and industrial installations.