plinth beam and plinth protection

What Is Plinth | What Is a Plinth Beam | What is Height of Plinth | What is Plinth Protection | Purpose of Plinth Protection

What Is Plinth?

Plinth is a base or platform that supports a plinth beam, columns, and structures. The function of the plinth is to distribute weight and pressure evenly across a column over a wider space.

The plinth is also used to elevate structures above the ground to ensure their protection from water and other surrounding elements.


What Is Height of Plinth?

The height of the plinth is between 300 – 450 mm below the bottom level, it is recommended that a minimum baseboard peak of 150 mm above the natural level be adopted.


What Is Plinth Level?

Plinth Level is a specific height from ground level at which building superstructure construction starts. Generally, the plinth level height kept between 300 mm to 450 mm.

What is a Plinth Beam?

Plinth Beams are constructed between the wall and its foundation and are reinforced concrete beams, these beams are provided when the foundation suffers from settlement to prevent the expansion or spread of cracks in the wall from the foundation and the foundation but these beams distribute the load of a wall.

What Is Plinth | What Is a Plinth Beam | What is Height of Plinth | What is Plinth Protection | Purpose of Plinth Protection
Plinth Beam

As we know, a superstructure is above ground level which includes beams, columns, masonry walls, and slabs, etc., and in this type of structure, the plinth beam splits the superstructure and substructure which acts as a tie beam. That keeps walls and columns linked.

Read More: 8+ Foundation Construction Steps


Purpose of Providing Plinth Beam

Following are the reasons for the providing the plinth beam,

  1. These beams in the structures prevent differential settlement and all the loads on the plinth beams are transferred equally due to the foundation.
  2. These beams prevent moisture from entering the building from the foundation.
  3. These beams bind all the columns.
  4. It prevents cracks from the foundation to the wall.
  5. This prevents the building to collapse during an earthquake.
  6. These beams distribute the load evenly.

Standard Dimensions of Plinth Beam

  • The width of the beam is usually 9 ″ or 225mm, as the wall width in India is 9 ″. So that the structure has a good look.
  • The minimum size of the RCC plinth beam should not be less than 9 “x 9” (225 mm x 225 mm), as a general rule of thumb.
  • The plinth beam size for a 1-story building is 9 “x 9” (225 mm x 225) mm) and is 9″x 12″ (225 mm x 300 mm) plinth beam sizes are used for 2 story (G + 1), 3 story (G + 2) and 4 story (G + 3) houses.

Applications of Plinth Beam

Following are the Applications of Plinth Beam,

  1. As per standards, it has made mandatory in earthquake-prone areas to construct plinth Beam.
  2. It is applicable to construct a plinth beam Above Ground Level.
  3. Plinth Beam carries the load of the wall constructed above it.
  4. Water from the surface is prevented to get implicated into the soil using Plinth Beam.
  5. The best application of a plinth beam is to withstand outside actions such as water, tree roots, termites which could affect the life of the plinth.

Concrete Grade Suitable For Plinth

Concreting of Plinth Beam
Concreting of Plinth Beam
  • Minimum of 20Mpa Strength is required for Plinth in order to withstand outside actions.
  • Manual Mixing of concrete needs 20% extra cement to be added to the mixture, for compensation of losses.
  • Proper installation is mandatory in the case of Formwork prior to the concrete filling.
  •  The strength of the plinth is well dependant on the adequacy of formwork secured while concrete filling.
  •  Concrete compaction is also one of the factors responsible for obtaining sufficient strength.

Read More: 25 Different Types of Beam In Construction & Their Use


Form Work and Steel Bars Used in Plinth

Formwork and Steel of Plinth Beam
Formwork and Steel of Plinth Beam
  • Two Reinforcement Steel bars with a minimum of 12mm diameter are required to be provided at bottom of a beam.
  • However, at the top, 10mm diameter steel bars are recommended for the plinth beams.
  • Along with the 12mm diameter bars at the bottom and 10mm diameter steel bars at the bottom, it is compulsory to provide a 25mm concrete cover for protection.
  • Spacing of 15 cm along with 6mm stirrup diameter is recommended as per standards.
  • Formworks are installed prior to concrete filling in an adequate manner to ensure and obtain the required strength of concrete.
  • Another important factor responsible for gaining the required strength is the compaction of concrete.
  • Concrete compaction eliminates the void ratio within the concrete after placement.

What is Plinth Protection?

Plinth Protection
Plinth Protection

Plinth protection is provided to prevent water implication into the soil and reach the equal of the plinth wall and floor by capillary action resulting in moisture, acting as a barrier and water in the ground near the plinth wall blocks direct access to.

Plinth protection is supported by offering an additional shape or additional thickness/peak under the beam or under the foundation. In short, the plinth is the base of the structure that carries the weight of the structure to the soil.

Many times, the plinth has to deal with outside actions such as water, tree roots, termites as it affects the life of the plinth and fails it, so it is necessary to protect the plinth from such activities.

Read More: What is Lintel Beam? Propose, Size & Types


Purpose of Plinth Protection

  • Plinth protection isnecessary to prevent the water leaking into the earth.
  • ·Plinth protection prevents water from entering the soil directly near the plinth wall, this is usually done by placing a plain precast slab width of 600 mm.
  • The purpose of a frame structure is to connect the plinth beam to all columns, reducing the efficient size and slope of the columns.
  • The welded beams commonly used in foundations are slightly deeper, acting as a reinforcement or mooring element.
  • Another reason for providing a plinth beam is to avoid different settlements in the building, due to the fact that the whole weight of the wall is below the skirting beam.
  • Fringed beams are typically used when the foundation is slightly deeper and thus serves as a reinforcement or mooring element.

FAQs

What Is Plinth Beam?

A Reinforced Concrete Beam built at a plinth level used to join all the columns and hence reducing the actual length in a frame structure is termed a Plinth Beam.
Plinth Beams are constructed between the wall and are provided when the foundation suffers from settlement to prevent the expansion or spread of cracks in the wall from the foundation.

What is the Size of Plinth Beam?

225MM X 225MM
The width of the beam is usually 9 ″ or 225mm, as the wall width in India is 9 ″.
The minimum size of the RCC plinth beam should not be less than 9 “x 9” (225 mm x 225 mm), as a general rule of thumb.


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