What is Plinth Beam? | What is Plinth?
Plinth beam is not a difficult building member. Actually Plinth Beam Definition: Plinth beam is a type of base/reinforced concrete beam which is generally constructed between building foundations to support superstructure components of building such as a wall, columns, slabs, etc., and in the type of structure, the plinth beam splits the superstructure and substructure which acts as a tie beam.
The primary function of plinth beam is provided to prevent or expansion of cracks in construction from the substructure of the building or footing structure design into the wall (Any type of the wall) above when settlement takes place in the foundation.
Plinth Beam
Why Plinth Beam is Provided?
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| Plinth Beam |
What is plinth beam means is now clear in your mind also a key function of plinth beam design which is the answer to why plinth beam is provided.
We provide a plinth beam to distribute any type of load of superstructure over the foundation evenly. The plinth is also used to create level structures surface above the ground to make sure their protection from water level and other surrounding elements.
Plinth Beam Height
The plinth beam height varies between 300 mm – 450 mm above the ground level surface, In plinth beam design it is preferable to the kept peak of 150 mm above the construction site ground level be adopted.
Standard Dimensions of Plinth Beam | Plinth Beam Size
Plinth Beam Size:
- The width of the RCC plinth beam is usually 9 inches or 225mm, mostly equal to wall width so that luxury architecture houses look not compromised. For example, the Plinth Beamwidth Size in India is 9″.
- As per the civil engineering thumb rule by expert civil engineers minimum size of the RCC plinth beam should not be less than 9“x9” (225 mm x 225 mm).
Example for Standard Dimensions of Plinth Beam | Plinth Beam Size:
The plinth beam dimensions for a 1 story building are in inches 9″ x 9″ or in mm 225 mm x 225 mm.
The plinth beam dimensions for a 2 story building is in inches 9″ x 12″ or in mm 225 mm x 300 mm also known as the design of a plinth beam for 2 stories (G + 1) building. Sometimes the same size of beams is used for 3 story (G + 2) and 4 stories (G + 3) houses.
Minimum Dimension of a Plinth Beam | Height of Plinth Beam
A minimum depth of plinth beam (height of plinth beam) is 20cm whereas its width should match the width of the final course of the foundation.
Plinth Beam Steel Details
- Steel Bars Used for Plinth Beam is recommended to provide two bars with a minimum diameter of 12mm at the bottom of the beam. Similarly, in the plinth beam, two reinforcement bars with a minimum diameter of 10mm shall be provided at the top of the plinth beam.
- Reinforcement bars should be protected by a 25mm concrete cover (Read the concrete cover detailed article from below also read link). As far as stirrups are concerned, the stirrup diameter should be at least 6mm and a spacing of 15cm should be sufficient.
- Another important factor responsible for gaining the required strength is the compaction of concrete.
Purpose of Plinth Beam
In civil engineering construction, the field plinth beam has many Purposes. The list of Purposes for Providing Plinth Beam is provided below.
The reasons for providing the plinth beam are:
- These types of plinth beam designs in construction prevent uneven settlement of the building and the load of the structure is safely and evenly transferred to the foundation.
- To prevent foundation to wall crack in the structure.
- These beams transfer structure components load evenly.
- By using a foundation plinth beam we can prevent moisture from entering the building through the foundation.
- Plinth beam reinforcement details help to prevent the building to collapse during an earthquake.
- These beams bind all the columns.
Concrete Strength Suitable for Plinth Beam Construction
Strength of plinth beam concrete is never smaller than 20MPa (M20 Grade of concrete: You can create a mix design by Excel Sheet). If concrete is mixed by manual method, then you should add an extra 20% cement during the mixture.
Plinth beam concrete ratio used as the minimum is 20MPa and the Plinth beam concrete ratio is 1:1.5:3 (Cement: Fine Aggregate: course Aggregate) so the purpose of the plinth beam is achieved.
Applications of Plinth Beam
Following is the list of Applications of Plinth Beam in the Civil Engineering field.
- Construction of the design of plinth beams above the natural ground is another application of this type of beam.
- As per standards code rules and dimensions, it has been made necessary in earthquake-prone areas to construct plinth Beam.
- It is applicable to construct a plinth beam Above Ground Level.
- Use and best application of concrete construction plinth beam are to withstand outside actions such as water, termites, tree roots which could affect the design life of the plinth.
- This beam is required to provide plinth beam foundation in areas that are prone to earthquakes.
- Water from the lower building surface is prevented to get implicated into the subsoil using Plinth Beam.
- This type of Plinth Beam carries the load of the wall constructed above it.
Formwork for Plinth Beam
Plinth beam formwork used for plinth beam in building construction should be properly installed and adequately secured prior to concrete placement. The concrete needs to be compacted sufficiently by using vibrators to prevent steel bars from aggressive elements.
What is Plinth Protection?
Plinth protection is adopted to prevent water from seeping into the soil and reaching the plinth wall and floor by capillary action, resulting in moisture, acting as a barrier, and water in the ground near the plinth wall blocking direct access to.
Plinth protection is supported by providing an extra design or thickness/peak beneath the beam or foundation. In a summary, the plinth is the structure's foundation that transfers the structure's weight to the earth.
Outside actions such as water, tree roots, and termites frequently impact the plinth's life and cause it to fail, hence it is essential to safeguard the plinth from such activities.
Purpose of Plinth Protection
- Plinth protection is always necessary to prevent water transportation into the earth.
- Fringed beams are generally used when the foundation construction is more depth and thus serves as a reinforcement or mooring element.
- The welded beams are normally used in foundations that are slightly deep and act as a mooring or reinforcement element.
- Another reason for providing plinth beam protection is to avoid uneven foundation settlements in the building, due to the fact that the total weight of the structure is below the skirting beam.
Process of Concreting in Plinth Beam
Construction of plinth work involves the following kind of work in Building Construction
- Casting of columns up to the plinth level.
- Constructing rubble/brick masonry up to the plinth level.
- The casting of plinth/tie beams at the designed level.
- Anti-termite treatment in foundation.
- Refilling of column pits and plinth with selected material.
- Soling over the compact refilled material.
- D.P.C. over plinth walls.
- Floor P.C.C.
- Plinth protection.
Casting And Checking of Columns up to Plinth
- After casting of footings is done, mark the center line of columns on the footing.
- Erect the column cage by checking the number of reinforcement bars, the diameter of bars, spacing, and type of links (rings).
- Provide the length of column bars up to the beam level, considering the appropriate lap length of the bars.
- Cast the column up to the plinth level or up to the bottom level of the tie plinth beam work procedure.
- Check the proper covering for column reinforcement.
- Check the unsupported height of the column for slenderness, from footing top to bottom of the beam. If the height is beyond limits, inform the Structural Consultant and provide an intermediate tie beam.
- Check the offsets of the column as per the drawing.
- Check the mix before casting.
- Maintain a proper water-cement ratio.
- Compact the concrete with a needle vibrator.
Plinth Tie Beams Work Procedure – Casting And Checking
- The plinth level is first finalized with respect to the parking ground level.
- The plinth beam work procedure can be cast by adopting the usual procedure of propping and shuttering.
- Tie beams may be cast on masonry work at the plinth level. The only side shuttering and supports are required in this case.
- The bottom of the peripheral plinth beam should be kept 15cm below the existing ground level and necessary plinth masonry should be done above the beam.
Checklist For Plinth Beam Work Procedure
- The size (b x d) of the beam.
- Reinforcement of the beam as per the structural drawing.
- Proper anchorage of the bottom and top bars in the columns.
- Length of continuation of bent bars and extra top bars over supports.
- The face of the column on which the beam rests (This confirms the room dimensions and any architectural feature if involved).
- The diameter of the stirrup bar and the spacing of the stirrups.
- The bottom and side cover for reinforcement are to be provided.
- Controlling the proportion of the concrete mix.
- Ensuring and checking of line, level, plumb, and supports of the shuttering.
- Plugging of all possible joints of shuttering from where the cement slurry may flow out while vibrating the concrete.
- Confirm the change in concrete grade for beams and columns (if any).
- Ensure the compaction of the concrete.
Plinth beam design Excel Sheet Calculation
Here Civil Experience provides two Examples of this beam design in excel through pdf in which final reinforcement bars calculation, CLEAR COVER TO BEAM,d' 40 MM, GROSS CROSS-SECTIONAL AREA OF BEAM, Ast REQ'D, DIA OF BAR (MM), NOS. OF BARS, Ast PROVIDED etc calculate for structure design of beams excel. You can download that pdf file of structure design beam excel calculation from below.
Checklist Of Plinth Beam Work
- Check the level of masonry work with respect to the plinth level.
- Check that all stub columns are cast (2″) above the plinth or up to the bottom of the plinth beam work procedure as required.
- Check the lap lengths provided for all bars above the plinth for adequate length.
- Check the faces of the columns on which the plinth beam rests.
- Reduction of columns, if any, should be done at the beam level only.
- Check the distance between masonry walls for room dimensions.
- Check the size of the plinth beams and the reinforcement of the same.
- Check the proper anchorage of plinth beam bars in columns.
- Check the shuttering/formwork of the plinth beam work procedure for alignment, level, plumb, and supports.
- Check and cast the beams and columns with the proper grade of concrete, ensuring the required covers to the reinforcement.
- Control the design mix of concrete, carry out the compaction by means of a vibrator.
- Cure the concrete/masonry work. Remove all grass shrubs and loose material from the plinth area.
- Fill the plinth with murum or approved excavated stuff.
- See that filling is done in layers, watered, and compacted, no layer being greater than 15cm to 20cm (6″ to 8″)
- Check and keep the proper sunks for W.C. bath and toilets.
- Over compacted filling, hand-packed rubble soling of proper thickness should be done.
- Check the quality of the soling material. Compact the soling and fill the gaps with chips.
- Get the side shuttering for P.C.C. and mark the exact level of the P.C.C. top.
- Take intermediate thiyyas and confirm the uniform thickness of P.C.C. throughout.
- Rectify the ups and downs, observed in the above points.
- Do the P.C.C. by hand mix/mixer.
- Compact the P.C.C. with a rammer.
- Level and finish the P.C.C.
- Check the drawing to see if the plinth is given or not.
- If yes, follow the procedure specified and complete the plinth protection.
- Construct the steps of the plinth (in masonry) keeping the margin for the floor finish. Do not confuse the plinth level with F.F.L. (Floor Finish Level)
We almost cover all points but some Advance materials like excel files for design beam, plinth beam drawing, plinth beam reinforcement design, difference between ground beam and plinth beam, plinth beam reinforcement calculation, plinth beam design excel sheet and many more for Expert Smart Civil engineers. But if you are happy like generally civil engineer, contractor, the consultant then this Civil Experience article is more than enough for you.
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FAQ 1: What is Plinth Beam?
Plinth beam is not a difficult building member. Actually Plinth Beam Definition: Plinth beam is a type of base/reinforced concrete beam which is generally constructed between building foundations to support superstructure components of building such as a wall, columns, slabs, etc., and in the type of structure, the plinth beam splits the superstructure and substructure which acts as a tie beam.
FAQ 2: What is Plinth Beam Height?
The plinth beam height varies between 300 mm – 450 mm above the ground level surface, In plinth beam design it is preferable to the kept peak of 150 mm above the construction site ground level be adopted.
FAQ 3: Why Plinth Beam is Provided?
What is plinth beam meaning is now clear in your mind also a key function of plinth beam design which is the answer of why plinth beam is provided.We provide a plinth beam to distribute any type of a load of superstructure over the foundation evenly. The plinth is also used to create level structures surface above the ground to make sure their protection from water level and other surrounding elements.
FAQ 4: What is Plinth Beam Size?
1. The width of the RCC plinth beam is usually 9 inches or 225mm, mostly equal to wall width so that luxury architecture houses look not compromised. For example, Plinth Beamwidth Size India is 9″.2. As per the civil engineering thumb rule by expert civil engineers minimum size of the RCC plinth beam should not be less than 9“x9” (225 mm x 225 mm).
FAQ 5: Plinth Beam Steel Details
[1.] Steel Bars Used for Plinth Beam is recommended to provide two bars with a minimum diameter of 12mm at the bottom of the beam. Similarly, in the plinth beam, two reinforcement bars with a minimum diameter of 10mm shall be provided at the top of the plinth beam.[2.] Reinforcement bars should be protected by a 25mm concrete cover (Read the concrete cover detailed article from below also read link). As far as stirrups are concerned, the stirrup diameter should be at least 6mm and a spacing of 15cm should be sufficient.[3.] Another important factor responsible for gaining the required strength is the compaction of concrete.
