What is a Plinth beam? Plinth beam height and size

What is a plinth beam in construction? Plinth beams are horizontal structural elements that are built at the plinth level. It is the first beam built after the foundation has been completed. Furthermore, the plinth beam is an important component in a building because it serves as a foundation for brickwork as well as a moisture barrier, preventing moisture from entering the superstructure walls. The height of the plinth beam is typically 200mm to 450mm. It can be both reinforced and unreinforced.

The most important components of a building are the substructure and superstructure. The substructure is the part of the building that is below ground level, while the superstructure is the part of the building that is above ground level. The plinth level separates the substructure from the superstructure. The plinth beam follows the foundation’s construction. This article discusses what a plinth beam is, as well as plinth level, plinth beam size, and plinth beam height.

  1. What is a plinth?
  2. What is a plinth beam?
  3. Plinth beam in construction – Functions and advantages
  4. Size of plinth beam
  5. Plinth beam reinforcement
  6. Plinth beam construction

What is a plinth?

The plinth is the structural stratum that separates the superstructure and substructure of a building. All structures must have a ground floor that is 45 to 60 centimetres higher than the surrounding ground. This will prevent rainwater, dirt, and dust from entering the building. Because of this, the outer dimensions of a pedestal constructed first are slightly larger than those of the ground floor. That is referred to as the Plinth. A level or base known as a plinth is used to support superstructure walls, columns, and other structures. The plinth’s function is to distribute pressure and load evenly across a surface.

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What is a plinth beam?

A plinth beam, as the name implies, is a beam at the plinth level. It is a particular kind of beam that is situated at the bottom of a framed structure. Because it holds the columns in place, it is also referred to as a Tie Beam. A horizontal structural component that joins the columns at the plinth level of the building is called a plinth beam. It is constructed above the top of the plinth level in load-bearing walls to aid in uniform load distribution and building settlement. Plinth beams reduce the length and slenderness ratio of a column. These beams are installed to prevent foundation cracks from spreading into the structure.

The plinth beam is located at 1.5 to 2 ft above Ground Level

Plinth beams are installed to stop cracks from the foundation from spreading into the wall above when the foundation settles. Plinth beams distribute the load of the wall evenly over the foundation.

Plinth beam in construction – Functions and advantages

Following are the functions and advantages of plinth beams

  • To prevent the development of cracks from the foundation to the walls
  • For distributing loads uniformly from columns to the foundations via superstructure.
  • Prevention of differential settlement
  • To prevent the entry of dampness in the structure. 
  • For avoiding the collapse of building due to earthquakes. It is crucial to provide plinth beams in earthquake-prone areas.
  • For providing support for walls
  • To reduce the effective length of columns. 
  • Prevention of column buckling
  • To withstand lateral forces. 
  • It saves buildings by preventing differential settlement which is caused by the partial failure of substructure or by the failure of soil on which buildings are constructed.
  • It provides uniformity to buildings at the plinth level.
  • The best application of a plinth beam is to withstand outside actions such as water, tree roots, and termites which could affect the life of the plinth.
plinth beam
plinth beam

Size of plinth beam

The plinth beams are designed in accordance with IS 132920-2016. According to the IS Code, the minimum width of the plinth beam cannot be less than 250mm. The depth should be not more than 1/4 of the clear span and not less than 200mm depth. In addition, the span to overall depth should be between 15 and 18. The concrete strength of the plinth beams shall not be less than 200Mpa.

Plinth beam
Plinth beam

Plinth beam reinforcement

At the bottom of the beam, two bars with a minimum diameter of 12mm are recommended. Similarly, two bars with a minimum diameter of 10mm must be provided at the top of the plinth beams. A 25mm concrete cover should be used to protect reinforcement bars. The stirrup diameter should be at least 6mm, with a 15cm spacing.

Plinth beam construction

1) Determining the mark-up width First, the plinth level is marked. Plinth beams are usually half the width of the foundation. The skeleton is prepared after marking the width of the plinth. The beam reinforcement must then be completed prior to shuttering.

2) Formwork Installation The next step is to put up formwork. Steel, wood, or plastic must be used for formwork. By levelling the ground, you can fix the formwork properly.

3) Concrete pouring Before pouring concrete, make sure the shuttering is dry and all the joints are tight.

4) Pouring of the concrete

Before pouring concrete, ensure the shuttering is dry and all the joints are tight. Pour the concrete evenly. 

5) Curing of the Concrete

After the concrete is dried, It is cured for at least 7 to 14 days for attaining good strength and durability

5) Removal of Formwork

After curing Once the concrete is set, remove the formwork. 

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