Metal becomes bigger when hot and smaller when cold. In this guide, the expansion gaps are explained to be calculated, as well as how to select materials such as aluminum or steel. All materials expand and contract due to temperature changes. It is important that cable tray installations incorporate features which provide adequate compensation for their thermal contraction and expansion. Cable tray system designs that do NOT take this. Is your cable tray system optimized for safety, dependability, space and cost savings? Cable tray (or cable ladder) systems are a popular alternative to electrical conduit systems, as they have an outstanding record for dependable service, design flexibility and cost savings in commercial and. All materials expand and contract due to temperature changes.