In Summary
  • Beams are a major part of construction projects whether residential, commercial, or public.
  • They provide support for floors and ceilings, and come in a variety of forms.

A beam is a structural element that provides support for floors and ceilings. Their main purpose is to transfer loads horizontally along their lengths to supports where the loads are usually resolved into vertical forces.
According to Ronald Atwiine, a structural engineer at Excite Construction, a beam is subjected to two sets of external forces and two internal forces. The external loads are those applied to the beam and reactions to the loads from the supports.
Beams are classified by their location in the structure and choosing the right one for the right location is very important for building safety.

Ring beams
Ring beams are structures that separate the windows from the roof, and enable the two to be fixed together at the required angle. They are usually made of concrete or reinforced steel and provide the tensile strength that brickwork lacks.
“They give structures supreme stability, where they would otherwise be rather unstable,” Atwiine explains. Although a ring beam will help to support the roof of your house, it is vital to make sure it will be able to do so, and you are not overloading the beam with more than it can take. This is why it is usually important to strictly follow the calculations the engineers recommend. “We have seen roofs cave in because the contractor wants to save money by using less of the recommended materials which is quite a shame,” Atwiine notes.

For reinforced ring beam, the ratio should be 1-2-4 (one bag of cement, two of aggregate and four of sand). The construction of the ring beam should at least be given about seven to 10 days to set. However, if immediate construction is a must, you need to have a proper concrete mixture and also ensure that support structures such as props are intact.
But when it comes to a storied house, it is important that you give the slab 21 days to set as you cure it by pouring water so that the concrete does not crack.

Ground beams
A ground beam is a reinforced concrete beam for supporting walls at ground level. Its purpose is to link the piles together and provide a platform for further superstructure construction. Atwiine says ground beams are very important in swampy areas where the foundation needs reinforcement.
“The ground beam is placed at the bottom and another layer added which will create a void between the ground and the underside of the beam to stop any pressure on the footings caused by ground heave,” he explains.
Below are other types of beams and their uses:

Ring beams are structures that separate the windows from the roof, and enable the two to be fixed together at the required angle. Photo by Eric Dominic Bukenya

Cantilever Beams
Cantilever beams are used in bay windows, bridges and balconies. They manage to redistribute the weight from whatever structure they are holding up to the main structural beams in the house or building to which they are connected.
In residential architecture, cantilever is often used for building balconies. In such structures weight is distributed onto the foundation beams. They are also known as end load beam type since the load is mostly supported on one side.

Flitch Beams
Flitch beams are made of steel plate sandwiched between two wood beams. They are designed to be strong as well as lightweight. Flitch beams are less expensive than pure metal beams as they are not made of solid steel. Flitch beams are created to support vertical loads.

I-Beams
I-beams are the most common types of beam designs used in construction. I-beams are columns that are straight in shape. They may be used to create long spans of support in roofs, walls and floors.

H-Beams
H-beam looks similar to the shape of the I-beam and there are some advantages to its design. The main difference between I-beam and H-beam shapes is the flange, which is wider in h-beams. They also have a bigger surface area on the cross section of the beam.
According to Atwiine, the choice of the beam depends on the architectural design. One may use cantilever beams or continuous beams for balconies. “But for storied buildings we must have ring beams and primary beams. Ground beams are optional depending on the bearing capacity of the soil. Otherwise buildings need to be tied at the bottom by ground beams and at the top by ring beams,” he says.

Generally different types of beams are applied in different buildings depending on the use, the design, the loading and the location. Also the size of the building matters for instance a hall may have bigger and heavily reinforced beams than just a bedroom and an office block would have bigger beams than a residential house.

Materials
Various types of materials such as wood, steel, aluminum, among others are used for constructing beams. The most commonly used material for beam is reinforced concrete cement.
The chosen material gives the beam its ability to withstand loads, to flex or compress without breaking, and to withstand heat, tension, shear, and other forces. Many materials change their length approximately linearly in response to an applied force.

For example if you imagine bending a square beam into an arc, the top edge must stretch and the bottom edge must compress.
The more the beam resists stretching and compressing, the harder it will be to bend the beam. An apt example is a piece of metal which will bend and not spring back while wood and concrete will break.

Tips to consider
Ring beams
•For reinforced ring beam, the ratio should be 1-2-4 (one bag of cement, two of aggregate and four of sand).
•The construction of the ring beam should at least be given about seven to 10 days to set
Ground beams
•These are important in swampy areas where the foundation needs reinforcement
Flitch beams

•These are created to support vertical loads.
•They are designed to be strong as well as lightweight
I-beams
•They also have a bigger surface area on the cross section of the beam.
Cantilever beams
•They are also known as end load beam type since the load is mostly supported on one side.