What’s In This Article?

In the world of civil engineering there are many types of concrete slab but the most important are:

  • One way slab and
  • Two way slab
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Both types of concrete roofing are quite strong, and each has its own strengths and weaknesses. However, the price of one way and two way roofing will differ quite a lot. So, it is essential to choose the one that you feel most comfortable with.

TIP! “Also remember that the thicker the concrete slab, the less the risk of deflection”

This article will explain how to recognize one way and two way slab with naked eye. First learn about the basics of these slabs and we will explain some quick points by which you will identify these with naked eye.

DESIGNING SPREADSHEETS – FREE DOWNLOAD
One Way Solid Roofing Design Spreadsheet Download Here
Ribbed Roof Design Spreadsheet Download Here
Flat Roof Design Spreadsheet Download Here
2 Way Slab Design Spreadsheet Download Here
One way roof design spreadsheet Download Here

What Is One Way Slab?

While designing or analyzing structure of concrete roofing, if bending is considered to be occurring in one direction only then it is called one-way slab. To be more clear see the diagram, below.

one way slab bending

A. On Which Condition It Is Used?

  • If roof is supported by beams on two opposite sides, no matter what the dimensions are, the it is designed as a one-way slab.

  • If it is supported by beams on all four sides, then we check the ratio of longer span(Lx) to shorter span(Ly). If this value is ≥2 then the roof is designed as a one-way slab. 

B. Examples Of One Way Slab

The best examples are:

  • Veranda
  • Car parking or garage
  • Long span hall

Now, lets get into the basics of two way slab.

What Is Two Way Roofing?

Similarly, if bending is considered to be occurring in both the directions then it is called 2 way slab. The diagram below illustrates it more clearly.

Two way slab bending

A. On Which Condition It Is Used?

If it is supported by beams on all four sides and the ratio of longer span(Lx) to shorter span(Ly) is less than 2, then the it is designed as a two-way slab.

B. Examples Of Two Way Roofing

The best example are:

  • Square shape are always two way.
  • Mostly used in residential

Difference Between One Way & Two Way Slab

Before concluding let’s summarize basic points which justify difference Between these two types:

difference between one way and two way slab

  • In this, a major portion of loads is carried along one direction. Whereas in 2 way slab load is carried along both the directions. See the figure below.

  • The (Lx/Ly) ratio is more than or equals to 2 in the one-way slab, whereas (Lx /Ly) is less than 2 in the two way.

How To Recognize One Way Slab With Naked Eye

  • It will be rectangular in shape.
  • Mostly, it has beam on two sides
  • The x-axis and y-axis length to width ration is greater than or equals 2.
  • Main reinforcement is provided in one direction only (short span)

Reinforcement of One Way Roofing

  • Main Reinforcement – It should be laid down in short span with alternate bent up bars.
  • Distribution Reinforcement – It should be laid down in long span on top of main reinforcement and no bent up bars.
  • Extra Bars – It should be laid down on top of bent up bars.

Conclusion:

Now, you are well aware about about two types of roofing. You’ll need to decide which types of roofingis best for your home.