What are the various diameters of the steel bars used in various structures

Steel reinforcement bars, commonly known as rebars or TMT Bars, are essential in reinforced cement concrete (RCC) structures. They provide necessary tensile strength to the concrete, which is strong in compression but weak in tension. Selecting the right diameter of the bars is critical for structural integrity, safety, durability, and cost effeciency. While the same standard bars are used across projects, their diameters vary based on the load-bearing requirements of different structural elements like slab, beam, column, and foundation.

Standard Diameter Available in the Market

In India and many other countries, similar standards such as IS 1786 for high-strength deformed bars, common TMT bar diameters include: 6mm, 8mm, 10mm, 12mm, 26mm, 20mm, 25mm, 32mm, 36, and 40mm.

Bars in slab

like in slab we generally use 8mm, 10mm , 12mm because load is less as compared to beam , column, footing.

note:- 8mm bar generally used in one way slab as distribution bar (secondary steel)

Bars in Beam

In beam we use bars having diameter Greater than 12mm (depends upon load)

Bars in Column

In column we use Greater than 12 mm (depends upon load)

Bars in Footing/foundation 

Similarly for footing we use 10 mm or more than that (depends upon loading)

Bars which are available in the market are 8 mm, 10 mm, 12 mm, 16 mm, 20 mm, 25 mm, 28 mm, 32 mm, 36 mm and 42 mm

Greater diameter like 64 mm and 128 mm has to be ordered specially from steel plant for manufacturing

Note:- 

Q 1 :- why we are not using 14 mm bar?

There is no specific reason for not using bar of 14,18, 22 mm etc diameter bar. I have mentioned the bars which are available in the market (India). As i mentioned in the first line of this post we use the bars which are available in the market.

Q 2:- How do we decide number of bars & which diameter of bars to use?

We decide the number of bars & diameter of the bars based on area of reinforced is required & convince of placing concrete.