Difference Between Joist and Beam

Joist and beam are among the most commonly used structural elements in the construction of a building.

They are used for different purposes and have a lot of different functions and properties, which make them suitable for specific requirements.

There is a lot of confusion between these terms due to their similar-looking structure.

Joist vs Beam

The main difference between Joist and Beam is that Joist is considered as the skeleton of any building that needs to span horizontally between the walls and the foundation of a building, whereas beams are structural elements that help in transferring load from the floor to the foundation through the columns and walls.

Joist vs Beam

Among the many structural elements used in the construction of a building, a joist is quite an important one. It is considered to be the skeleton of the building.

These are also regarded as small size beams running parallel to support the floor or ceiling.

The beam is also a structural element that is used widely in the construction of any kind of building. They help in transferring load to the foundation walls via roofs, walls, and columns.

Designer horizontal in orientation but can also be altered to serve a different purpose.

Comparison Table Between Joist and Beam

Parameters of ComparisonJoistBeam
AboutThese are structural elements that are like small beams and build the foundation of a building.They are structural elements used to transfer load from floor to foundation through columns.
SizeThese are smaller in size than beams.These are bigger as compared to Joists.
UseJoist is used for the skeleton of any building.The beam is used for transferring loads from floor to foundation via columns.
RoofRoof joists transfer load to vertical members.A roof beam is a kind of load-bearing member.
Strength to weight ratioThe strength to weight ratio is higher in joists.The strength to weight ratio is a little low in beams as compared to joists.

What is Joist?

Construction of a building is very extensive and a task that needs to be done with the utmost care-full measures. It involves the usage of a lot of structural elements along with lots of water, bricks, and cement.

One such important element is a joist. These are also sometimes considered as small-size beams due to their similar appearance to a beam and a comparatively smaller size.

It is a horizontal structural member that has a primary function very similar to a beam. It runs parallel across an open space.

They usually support a floor or ceiling by running between the walls. The dead load of the flour and sub flour is transferred to the foundation, walls, beams, and headers.

This dead load also includes the load of furnishings and people at all times. Therefore, a Joist needs to be structurally strong, and so the strength to weight ratio in Joists is quite high.

There are also roof toys that help in transferring the load of the roof to the vertical members.

Joist spans short distances as compared to beams and are typically made up of Wood, Steel, or sometimes even engineered wood.

What is Beam?

The other important structural member of a building is the beam. These are very commonly used, and almost everyone from the construction crew to the general public knows about beams.

The properties and nature of beams are extensively studied under civil engineering degrees and physics majors.

Beams are horizontally oriented, structural members who are widely used in order to transfer loads from ceilings, roofs, and floors to the foundation of the building through walls and columns.

The transferring of load plays a very important role in keeping the building intact and standing.

The size of beams is very big as compared to joists. Also, floor joists are laid directly on the beams. Sans walls and columns lay on the floor. They typically rest on the beams indirectly.

The very basic function of beams is to give a level and straight surface. This supports the floor joist system that is present between the foundation walls.

These are typically made up of steel or wood, but sometimes engineered wood is also used. The roof beam is a kind of load-bearing member.

‘Girder’ is a term that is often used in place of the term ‘beam’ in places where residential buildings are being constructed.

Main Differences Between Joist and Beam

  1. The joist is a structural element that makes up the skeleton of a building, whereas a beam is a horizontal structural unit that helps in transferring load to the foundation.
  2. The size of the beam is big as compared to the joist and, therefore, many times is also called a small size beam.
  3. The strength to weight ratio of the joist is higher. And in beams, it is lower as compared to the joist.
  4. Joist is considered to be an important element for the formation of the skeleton of a building, while a beam is important to transfer loads from floats and routes to the foundation of the building.
  5. Roof joists are used to transfer loads to the vertical members, whereas a roof beam is considered to be a load-bearing member.


The correct use of joist, as well as beam, is important to build a strong structure.

These are used in the construction of almost all kinds of buildings, and therefore a thorough knowledge of joist and beam is important for a civil engineer. A small mistake can lead to a big accident that can’t be avoided.

The right kind of beam or joist to be used at a place must be known so that the structure of the building remains strong and sturdy for a long time.

In short, Joists can be regarded as parallel series of structures that support a ceiling or floor, whereas beams can be considered as structural elements that carry the load to the foundation walls.


  1. https://www.sciencedirect.com/science/article/pii/S0141029608000242
  2. https://www.sciencedirect.com/science/article/pii/S0141029613006226
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