What factors determine the appropriate size and placement of cribbing and mats under outriggers?

• A. Crane weight, soil bearing, and manufacturer guidelines
• B. Aesthetics and color of mats
• C. Time of day and weather only
• D. Operator's personal preference

Answer: (C)

Sizing and placing cribbing and mats under outriggers is about safely transferring the crane’s load to the ground. The most important factors are how heavy the crane and its load are, the ground’s ability to support that load (soil bearing capacity, moisture, and stability), and what the crane manufacturer requires for outriggers, mats, and cribbing. Heavier loads or wider outrigger spreads increase the required contact area and strength, so larger or more cribbing and appropriately rated mats are needed to prevent sinking or tipping. If the ground is soft or wet, bearing capacity drops, which may call for thicker or additional cribbing and properly sized mats to spread the load over a larger area. Manufacturer guidelines provide model-specific minimum sizes, configurations, and stacking limits to ensure the setup matches the crane’s design. While weather and ground conditions can influence how the ground behaves, they don’t determine the size and placement by themselves—the weight, ground bearing capacity, and the prescribed guidelines do.