On most multi-storey schemes, the tower crane strategy is the logistics strategy. Get the crane positions right and deliveries, laydown, hoists and phasing fall into place. Get them wrong and the site spends two years working around them.
Start with coverage
A crane should reach every part of the building it serves, plus the areas where materials arrive and are stored. That usually means:
- the full footprint of each building, including scaffold and edge protection
- the laydown area and any loading bay
- skips and waste areas where the crane will lift them
- the heaviest lifts at the radius they will happen, not just at the tip
Check coverage against the load chart, not just the jib length. Precast panels, steel and plant often sit at the limit of a crane's capacity at mid radius.
Internal or external
A crane inside the building footprint, usually in a lift shaft or through a slab opening left for it, gives the best coverage with the shortest jib. The cost is a structural opening to infill later and a crane that has to come down before that area can be finished. An external crane is simpler to remove but needs a longer jib and takes up ground that is often scarce. On tight urban sites, internal cranes are often the only way to reach the whole building.
Keep cranes away from welfare and public areas
Loads should not pass over welfare cabins, offices, site entrances or public footways. Plan welfare outside the crane radius where you can. Where a radius has to cover a public area, the logistics plan should show slew restrictions or exclusion zones.
Two or more cranes
Where crane radii overlap, the plan needs an anti-collision approach. That usually means:
- height separation, with one crane set higher than the other
- zoning so jibs cannot enter the same space
- an electronic anti-collision system
Lifting operations are governed by the Lifting Operations and Lifting Equipment Regulations 1998, and BS 7121 is the recognised code of practice for the safe use of cranes.
Oversailing
In England, a landowner's rights extend to the airspace needed for the ordinary use of their land. A crane jib or counterweight swinging over a neighbour's property without consent is a trespass, and the courts have granted injunctions to stop it. In practice, that means an oversail licence, usually with a fee, insurance, an indemnity and restrictions on hours or loads.
Oversailing a public highway needs permission from the highway authority, usually the local council. Many councils run a specific tower crane oversail licence.
Oversail agreements can take months and neighbours are not obliged to agree. Identify every property and road inside each crane radius early, at planning or tender stage, so the crane strategy does not depend on a licence that never arrives.
What to show on the logistics plan
- each crane's position, jib length and radius, labelled
- the base, and whether the crane is internal or external
- areas of overlap, with the anti-collision approach
- oversail areas over neighbours and the highway
- slew restrictions and no-lift zones
- laydown and loading areas within reach