What is a Cantilever Beam?

A. Leverkuhn

A cantilever beam is a beam that is only supported on one of its ends. The beam bears a specific weight on its open end as a result of the support on its enclosed end, in addition to its structural integrity. Cantilever construction is popular in many kinds of architectural design and in other kinds of engineering, where professionals use terms like end load, intermediate load, and end moment to identify how much a cantilever beam will hold. The term moment is related to torque and to a theoretical load on a beam.

Cantilevers are the foundation of some bridges.
Cantilevers are the foundation of some bridges.

In residential architecture, cantilever design is often used for creating balconies and other extensions above ground level. Famous architects like Frank Lloyd Wright were known to take advantage of cantilever beam construction to provide for parts of a building that protrude from a supported section. The use of cantilevered setups and similar cantilever engineering is also often seen in bridges and similar projects. Carpenters might think of cantilever design in terms of wooden beams, but in other kinds of projects a cantilever design is applied to a concrete slab or a metal girder.

Typically constructed on steel and concrete, cantilever bridges can hold heavy loads, such as constant automobile traffic.
Typically constructed on steel and concrete, cantilever bridges can hold heavy loads, such as constant automobile traffic.

A specific use of cantilever beam construction is often part of a temporary construction project. While a bridge or other project is in transition, cantilever design provides for structural integrity while only one side of a beam is supported. Later, that beam may be supported on both sides. Engineers can show diagrams of how cantilever design will help ensure stability mid-way through a building project as part of a safety study.

Architects and engineers also use cantilever beam structures for the overhangs that are often a part of various buildings. Airports, university campuses, office complexes, and other areas will often include exterior structures that use cantilever beam construction for different intentions in building design. These overhanging elements can provide shelter from the elements or a decorative aspect to a building. In some cases, an "open style" cantilever design fits into a modern or artistic design for a space, where planners have blended practicality with aesthetic appeal.

Those who are interested in observing how cantilever design is used in modern engineering can easily find many visible instances of this engineering method at work in their local communities. A detailed study of this kind of design can better prepare a student for entrance into an engineering or architectural program. It can also increase a student's understanding of how professionals implement this kind of design to both residential and commercial projects.

Architects often incorporate cantilever beam structures into the overhangs that are a part of various buildings.
Architects often incorporate cantilever beam structures into the overhangs that are a part of various buildings.

You might also Like

Readers Also Love

Discussion Comments


What is the safe method of loading on a cantilever?


What are the applications of a cantilever beam, please?


I have always thought cantilever designs on buildings were intriguing. Any time I am standing on a balcony or overhang or something, I am always wondering what is holding me up. Most of the time it is pretty simple to look around and see the supports, but I have been in some buildings where the architect was creative and might have put the supports between floorboards or something so that it looks like the balcony is just sort of floating,

On the other hand, sometimes you can look around and find the supports and wonder how long they are going to hang on!


@Izzy78 - I am sure there are complex formulas, but I don't think you could really have a constant for a cantilever. The amount of weight it could hold would depend on too many factors. Namely, you would have to find some way to take into consideration the material of the beam and how it was attached to its surface. Also, you would need to know if the cantilever beam had a uniformly distrubuted load. Putting more weight on the end would have a different effect than putting weight closer to the wall.


@TreeMan - That is a good point, I never really thought of a crane as a cantilever, but I can see what you mean.

Is there any specific cantilever beam theory? Like, are there any formulas that will help to predict whether or not a cantilever is going to be able to hold a certain amount of weight?

I remember when I was in school, we had to do a project for a physics class one time where we only got a few things like plastic straws and toothpicks and tape and such, and we had to build a cantilever to hold as much weight as possible. It was challenging, but fun.


I guess I never realized how common cantilevers are all around us. Whenever I thought of them, I always just thought of things like lighted signs that hang off the side of a building. I guess balconies and things like that are pretty common, too, though.

Does a cantilever beam have to be perpendicular to the thing it is attached to? I was just thinking that the article talks a lot about the finished projects that use cantilevers, but it seems like the crane that builds the projects would also be a cantilever, since it is basically a steel beam that is extends from the main part of the machine.

Post your comments
Forgot password?