Using Concrete in Beam Design

Using Concrete in Beam Design

From designing single beams to huge projects, you need to consider what material you want to use and why. In this article, we discuss the advantages and disadvantages of using concrete as your base material for your beams in your next building project.

What is a Beam?

Wooden beam design over a half-built house

A beam is a horizontal part of a structure that spans over an open space and is supported near its ends. Specifically, a beam is an element of a structure whose width is no more than five times its depth. Anything wider as a structural element is a slab. A concrete beam is something which carries a load on itself vertically and withstands load primarily by resisting bending. A slab usually carries a uniformly distributed weight horizontally, by contrast. Slabs from the floor or roof of a building, while beams more often used where large concrete slabs are impractical.

Beams are often also referred to as ‘post and beams’ since beam construction relies on a floor built from concrete supports secured into the land below the structure.

When you put a weight on a flat object, the weight causes the beam to bend. When a beam bends, two things happen: the top of the beam is compressed and tries to get shorter, while the bottom surface is in tension, and tries to get longer. You can visualise this by stretching out your arm and pushing down on the inside of your elbow joint: the inside of your arm bends towards itself, which is compression, while the outside of your arm pushes out, which is tension.

Concrete beams have high compression and low tensile strength, which means that when pressure is exerted on concrete, eventually a crack will form at the bottom of the beam and progress upwards. Alternative beam materials like steel are more flexible. However, what is suitable depends entirely on the project at hand.


Advantages of Using Reinforced Concrete in Beam Design

Reinforced concrete beam design, black and white photo

Can be Cast into Any Shape

The main advantage of reinforced concrete over other building materials. You can immediately shape concrete into whatever form you desire.

Has Great Fire and Water Resistance

Concrete loses its structural integrity much less quickly than steel or wood when subjected to heat, and much more effectively resists fire. Concrete also better resists water than most alternative beam materials – it does not sag and lose strength like wood or corrode like steel. While certain chemicals in water can damage concrete, reinforced concrete is much more immune to damage.

Is a Low-Maintenance Material

Because concrete does not corrode, it does not need to be painted or regularly maintained in the same way that steel or wood or other materials might. This is especially true when exposed to the environment: concrete lasts much longer.

Has a Very Long Service Life

Reinforced concrete can last for decades without experiencing significant wear and tear. By contrast, alternative materials like wood require constant maintenance to remain their aesthetic and monetary value.


Disadvantages of Reinforced Concrete Beam Design

Concrete beam design over the foundations of a building

Has a Very Low Tensile Strength.

Concrete, as already discussed, has a very low tensile strength. This means when pressure is exerted, the bottom is likely to rotate and break, damaging the entire structure. As such, you typically need something with a higher tensile strength like reinforced steel bars to counteract the development of tension in concrete structures. This prohibits using concrete in a lot of projects.

Requires Shoring and Forming

Concrete needs a lot of shoring and formwork to safely and effectively mould the concrete into the shape you need for the project. This process can raise the cost of concrete structure immensely, especially where labour costs are high, and can constitute up to half or more of the cost of a structure. This can make using concrete prohibitively expensive if a very large number of beams are needed.

Need to Take Care When Creating Concrete

When you create concrete, you have to make sure that you correctly mix and proportion the material you are using. The mechanical and physical properties of concrete are sensitive, so if you are not especially observant about how the concrete beams are made and following the right processes, you might end up with overly weak or strong beams.

Results in Heavy Structural Elements

Reinforced concrete is heavier than wood or steel building materials. This means you have larger dead loads for your project – higher intrinsic weight in your structure – which in turn means larger foundations to support that extra weight.


The different advantages and disadvantages mean that depending on your project, your beam design has to be different. We have undertaken a number of projects where we have designed beams to support a new house’s construction. So, if you need any support, please do not hesitate to get in touch and our team will be happy to help.

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