Temporary Works for Crane Bases

Crane bases are temporary structures that support mobile, tower, and crawler cranes during lifting operations.
The base must transmit the crane loads safely to the ground without excessive settlement or bearing failure.
Ground conditions must be assessed by a geotechnical engineer before the crane base is designed.
Common crane base types include timber mats, steel plates, reinforced concrete pads, and compacted granular platforms.
Outrigger pad loads for mobile cranes can exceed 100 tonnes per leg at maximum radius lifts.
Crane base design is a temporary works activity requiring design, checking, and approval through the TWC.
Settlement monitoring may be required during crane operation, especially on made ground or soft soils.
Underground voids, services, and drains beneath crane bases can collapse under the imposed loads.
The crane base must remain effective throughout the entire duration of crane operations on site.
Removal of the crane base must also be planned and managed as a temporary works activity.

Crane collapse	Inadequate crane base design causes ground bearing failure, outrigger punch-through, and catastrophic crane collapse.
Load transfer	Outrigger loads are enormous — the base must spread these loads to prevent local ground failure.
Legal requirement	BS 5975 and LOLER 1998 require crane bases to be designed, checked, and managed as temporary works.

Do

Don't

Commission a ground investigation to determine bearing capacity at the crane location
Design the crane base through the temporary works procedure with TWC approval
Verify the base construction matches the approved design before the crane arrives
Check for buried services, drains, and voids beneath the proposed crane base area
Monitor settlement of the crane base during operations, especially on first use
Ensure outrigger pads are positioned centrally on the designed bearing area
Maintain the crane base surface in good condition throughout the duration of use
Brief the crane operator on the base design capacity and any load restrictions
Record all inspections and monitoring data in the temporary works register
Plan and manage removal of the crane base as a temporary works activity

DON'T position a crane on unassessed or undesigned ground bearing surfaces
DON'T exceed the design load capacity of the crane base at any outrigger position
DON'T set up cranes over buried services or drainage without engineer assessment
DON'T skip the TWC approval process for crane base temporary works
DON'T use timber mats that are damaged, split, or undersized for the applied loads
DON'T ignore signs of settlement, cracking, or displacement in the crane base
DON'T allow water to pond on or undermine the crane base — maintain drainage
DON'T assume one base design suits all crane setups — each configuration needs review
DON'T allow other plant to track across the crane base and damage the surface
DON'T remove the crane base without a planned method statement and TWC involvement

See also: Temporary Works Awareness | Lifting Operations Awareness (LOLER)

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