When is the use of mats or cribbing typically required?

• A. Only when the ground is perfect.
• B. On soft or uneven ground or when the outrigger footprint would penetrate or settle deeply, to distribute load and prevent settling.
• C. Never necessary.
• D. Only for indoor lifts.

Answer: (B)

Distributing the crane’s load to protect the ground and keep the setup stable is what mats or cribbing are for. They are typically required when the outriggers would press into soft ground, settle into uneven surfaces, or create a point load that could cause tipping. By spreading the load over a larger, flatter area, mats or cribbing reduce bearing pressure, prevent sinking, and help keep the crane level and stable during the lift.

This matters especially on soft soils like mud, loose sand, or clay, or on uneven pavement, gravel, or ground with holes or gaps. Cribbing stacks or mats fill irregularities and create a solid base, while they must be rated for the crane’s weight and placed to avoid gaps.

Mats aren’t limited to perfect ground, nor are they only for indoor lifts or never needed; they’re a safety measure used whenever the ground can’t safely support the outrigger load.