Last edited 02 Sep 2016


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A cantilever is a beam supported only at one end, with load carried over the overhanging. This is in contrast to a simply-supported beam, which is supported at both ends.


Cantilevers provide a clear space underneath the beam without any supporting columns or bracing.

Cantilevers became a popular structural form with the introduction of steel and reinforced concrete. They are used extensively in building construction, notably in:

  • Cantilever bridges.
  • Overhanging elements and projections.
  • Balconies, such as at Frank Lloyd Wright’s ‘Falling water’.
  • Machinery and plant such as cranes.
  • Overhanging roofs such as stadium roofs, and shelters.
  • Shelving.
  • Furniture.

Cantilever construction can be used in bridge building for crossing large spans. A simple cantilever span is constructed from two cantilever arms extending from opposite sides, and meeting in the middle. A common variation of this is the suspended span where the cantilever arms support a central truss bridge resting on the ends of the cantilever arms. A classic example of the cantilever bridge is the Forth Railway Bridge in Scotland which has three cantilevers with two connecting suspended spans.

Cantilever cranes (otherwise known as “hammerhead crane”) are hoisting cranes with a swing or fixed cantilever along which a hoisting trolley moves. They are often used in shipyards and during the construction of tall buildings.

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