The NEC requires that cable trays must be supported by members at an interval specified by the cable tray manufacturer, but not more than 5 feet for horizontal runs to support the weight of the cables and other loads. The NEC has a requirement for ladder-type cable trays. Clause 522-08-04 Where conductors or cables are not supported. us-trations without notice. The mechanical and electrical characteristics, tests, certifications, overall quality management, recommendations mentioned. A 10 or 12-foot cable tray is usually used for both of these installation types. Bearers shall be spaced evenly along the length of the bundle.