# One Way Slab and two way slab – 20 Major Differences

One way slab ratio is equal or greater than 2 and usable where the load is carried in one direction. On the other hand, the two way slab ratio is less than 2, more durable, and usable where the load is carried in two directions. There are many types of slabs but mostly utilize the two basic varieties of slabs one way slab and two way slab.

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However, the use of these two slabs according to their quality affects a building’s overall strength, functionality, and efficiency. In this article, we will discuss the one way and two way slab difference.

## What is a slab?

Slabs are constructed or provide flat surfaces, usually horizontal, in * building floor roofs*, bridges, and other types of structures. Each type of slab has its unique slab beam design.

The slab may be supported by walls, and reinforced concrete beams are usually cast monolithically with the slab, by structural, ** steel beams**, by columns, or by the ground. The depth of the slab is usually very small compared to its span.

## How many Types of slabs?

Here are the most commonly used types of slab:

- One Way Slab
- Two Way Slab
- Composite slab
- Ribbed slab
- Hollow core slab
- Flat slab
- Waffle slab
- Pre-stressed slab
- Slab-on-grade
- Post-tensioned slab

## What is the difference between One Way Slab and Two Way Slab?

These two types of one way two way slab are most commonly used in floor systems. Identifying the differences is difficult but in an easy way you can easily understand the difference between one way and two way slabs. Let’s drive them.

One Way Slab | Factor | Two Way Slab |

Bends only in one shorter direction. | Bending Moment | Bends in both shorter and longer directions |

Cylindrical | Deflected Shape | Dish or Saucer |

Beams on two opposite sides | slab beam | Beams on all four sides |

Loads are carried along one direction. | Load Carrying Direction | Loads are carried along both directions. |

Main reinforcement is provided in the shorter direction. | Reinforcement | Main reinforcement is provided in both directions. |

Slab thickness is more. | Slab thickness | Slab thickness is less. |

Economical up to a span of 3.6m. | Span | Economical for the panel sizes up to 6m x 6m. |

Longer span(l) /Shorter span (b)>= 2 | one way and two way slab formula | Longer span(l) /Shorter span (b)<2 |

The depth of the slab increases | Depth | The depth of the slab decreases. |

Slabs are suitable for smaller spans. | Span Length | Slabs are suitable for larger spans. |

Construction of slabs is easy. | Construction Complexity | The construction of slabs is more complex. |

Less steel | Quantity of Steel | More steel |

For shorter spans, slabs work well. | Span Length | For larger spans, slabs work well. |

Column sizes with the same span may be smaller. | Column Size | Column sizes may be significantly affected by labs because of the two-way load distribution. |

One Way Slabs have a lower load capacity | Structural Efficiency | Two Way Slabs are more efficient than One Way Slabs |

## What is the One Way Slab and Two Way Slab Formula?

Now, we will explain the one way two way slab formula with examples.

### One Way Slab formula:

The ratio of a larger span to a shorter span is greater than or equal to 2.

Longer span(L) /Shorter span (W)**≥ **2

### Example:

L= 6

W= 3

L/W=6/2=3>2

### Two Way Slab formula:

The ratio of longer span to shorter span is less than 2.

Longer span(L) /Shorter span (W)<2

### Two Way Slab Example:

L= 3

W= 2

L/W=3/2=1.5<2

## What are the applications of the One Way Slab and the Two Way Slab?

The applications of the one way slab vs two way slab depend on several factors like location and load.

Applications of One Way Slab | Applications of Two Way Slab | |

Residential Buildings | Commonly slabs are used in small residential buildings and commercial buildings. | Commonly slabs are used in large residential buildings and commercial buildings. |

Span Structures | Slabs are mostly usable in small structures where the load is carried in one direction. | Slabs are mostly usable in large structures where the load is carried in two directions. |

Usage | They are utilized for decks, roofing, and floor slabs. | These slabs are utilized for floor surfaces in multi-story structures and on bridges. |

## What are the advantages and disadvantages of the One way slab vs Two way slab?

Now, we discuss the pros and cons of the one way slab two way slab.

One Way Slab | |

Advantages | Disadvantages |

One way slab is more cost-effective because of its simple design and minimum reinforcing requirements. | One way slabs are not strong in the transverse direction. |

Designing and constructing the slab is too simple. | They might be more prone to warping and cracking, which might affect the building’s structural stability. |

Load distribution is only supported in one direction. | The capacity to support the load is lower as compared to the other types of the slab. |

Over time, one-way slabs are comparatively simpler to maintain and inspect. | The most effective use of one-way slabs is for shorter spans; as the span length grows, so does its efficiency decrease. |

Highly utilized in the small buildings. | Not suitable for irregular shapes and buildings with heavy loads or high lateral loads. |

Two Way Slab | |

Advantages | Disadvantages |

Slab distributes the load in both directions. | The design of the slab is complex. |

In architectural design, two-way slabs offer more versatility. | This requires a skilled worker. |

Due to their enhanced load-carrying capacity, two-way slabs can span longer distances. | Construction costs are somewhat high. |

More fire resistance is offered by two-way slabs than by other slab systems. | The necessity for perfect formwork makes construction more difficult sometimes. |

Don’t block the light’s reflection. | needs to be carefully designed since it could be susceptible to punching shear near supporting columns. |

## Which is better, one way vs two way slab?

One way slab and two way slab both of them have their own advantages and disadvantages. However, both are useful depending on the value of L/W, slab load, Construction restriction, architectural specifications, and span.

A one-way slab may be more suitable for shorter spans where simplicity, as well as affordability, are high desired outcomes. A two-way slab might be the better choice for longer spans and more sustainable material allocation.

A balance between structural efficiency, cost, and construction practicality frequently plays a role in engineering decisions.

## Frequently Asked Questions:

### How do you calculate one way or two way slab?

Simply, you can calculate the ratio of the one way slab and the two way slab. If the ratio of a longer span to a shorter span is equal or greater than 2 it is a one way slab. On the other hand, if the ratio is less than 2 then the slab is two way.

### Will a square slab behave as a one way slab?

Simply, when you see, the slab is supported along 2 opposite edges then the slab behaves as the one way slab.

### Which slab is designed as a two way slab?

The RCC roof slab is designed as a two way slab.

## Conclusion:

Slab design is an **important element in structural engineering**. One Way Slabs and Two Way Slabs are mostly used in construction structures due to their unique properties. Hope you understand the one way two way slab difference.

However, there is a fundamental difference between one way two way slab ratio and load distribution.