Outrigger

An outrigger is one of the hydraulic legs a mobile or vehicle-loading crane extends to spread its load and stabilise itself for lifting. Outriggers need confirmed ground bearing and properly sized pads under them, because an outrigger punching through soft ground is a classic crane incident.

When a mobile crane sets up, it lifts its weight (and the load’s) off the wheels and onto the outriggers, concentrating very high point loads through each foot. Two things have to be right:

• Fully deployed: the outriggers must be extended to the configuration the crane’s load chart assumes. A crane set up on partly-extended outriggers has far less capacity than the operator may read off the chart.
• Adequate ground bearing: the ground (and anything below it) must carry the bearing pressure under each foot. Pads or mats spread the load to within the soil’s capacity, and the set-up must account for soft or filled ground, recent trenches, edges, and especially slabs over basements or services that the point load could punch through.

That ground question is the most common crane-stability failure: the outrigger sits on what looks like solid ground but is fill, a service trench, or a basement slab, and it sinks or breaks through, and the crane tips.

For a builder the practical points are to know where the crane will set up early, to identify any basement, services, retaining wall or filled ground in the outrigger footprint, and to make sure the crane company’s lift plan confirms the ground bearing and the pad sizing. If the crane is setting up over a structure (a basement, a podium), the structural capacity for the outrigger loads has to be checked by the engineer, not assumed.

Also known as: Crane stabiliser leg, outrigger float (the pad).

Category: WHS / Cranes and lifting.

Related

• Crane / Hiab operator
• Lift plan

See also

• Dogger

References

• Safe Work Australia: cranes (verified 2026-06-03)

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Last updated: 2026-06-03. Verified: 2026-06-03. Quarterly review for currency.