How Do Tower Cranes Build Themselves Taller?

A tower crane is assembled on site, often with the help of a mobile crane, starting from a concrete foundation. To gain height, a climbing frame fitted around the mast uses hydraulic rams to raise the upper part of the crane, including the jib and operator cab. This opens a gap into which the crane lifts a new mast section, typically a few metres tall, and bolts it in place. Repeating this process lets the crane rise as the building grows. For very tall towers, cranes may climb inside the building's core, supported by the floors themselves.