Step by Step- RCC roof Slab steel calculation- Numerical Example

In this article, I have described step by step RCC roof Slab steel calculation. So read it carefully one by one to get a clear understanding.

Slab is a structural member which enable people to move from one floor and one place to another place in a flat. With out slab one can not take benefit of any structure like, building, culvert, bridge. etc.

What is RCC Slab?

Simply, the slab in which steel bars are used is known as RCC Slab. The full form of RCC is reinforced concrete cement. Where Reinforcement is called a steel rod.

The slab should be strong enough to bear the required load according to design. The slab should be provided steel bars to withheld tensile force, so this slab is called the RCC slab.

I have given an example for the calculation of the quantity steel rod in slab below.

rcc roof slab steel calculation

Let us take an example of a slab.

Numecal for RCC roof Slab steel calculation

Q) The length and breadth of slab is 10 meter and 7 meter respectively.

Let, The shorter span has provided the main rod and longer span has provided distribution rod.

Beside this the slab has following information,

For main bars
Length of on rod = 7 meter
Diameter = 12 mm
Center to Center gap (c/c) = 5 inch

For Distribution bars
Length of on rod = 8 meter
Diameter = 10 mm
Center to Center gap (c/c) = 5 inch


Remember that, slab does not have bent up bar. It means the slab only has straight bars. But, don’t worry you can calculate that also in the same process.

Bent up bar is also called crank bars which are in sloped form at the edge of the slab. you can see in this picture below.

RCC roof Slab steel calculation
Crank Bar or Bent up Bar

Now you have to see the calculation carefully to understand step by step.

Step:- 1

Calculate no. of Steel bar

For the main bar,

= L”/(c/c) + 1

= (8/0.127) +1

= 63.99

You can provide 64 bars

Now, For Distribution Bar

= L/(c/c) + 1

= (7/0.127)+ 1


You can Provide 57 bars


Calculate total length of steel bars

For main bars,

= 64 * Length of one Main Rod

= 64* 7

= 448 m


For distribution bars ,

= 57* Length of one Distribution bars

= 57* 8

= 456 m


Calculate weight of Steel bar

For main bar,

={(D^2)/162} * L

= {(12^2)/162} * 448

= 398.2 kg

Keep in mind that unit of Diameter (D) must be in millimeter and Length (L) must be in meter. And final result will be in Kg.

For Distribution bar

W = {(D^2)/162} * L

= {(10^2)/162} * 456

= 281.48 kg

Hence, in this way you can calculate weight or quantity of steel rod in a slab.

Watch video for better understanding

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"Structural Engineer" with over 5 years of experience in estimation, structural design, and surveying. I am passionate about using his skills to create safe and sustainable structures. I am also a keen writer, and I enjoy sharing my knowledge and experiences with others.

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