Difference Between One Way Slab And Two Way Slab

What is a slab?

Structural Concrete Slabs are constructed to provide flat surfaces, usually horizontal, in building floors, roofs, bridges, and other types of structures. The slab may be supported by walls, by reinforced concrete beams usually cast monolithically with the slab, by structural steel beams, by columns, or by the ground. The depth of a slab is usually very small compared to its span.

What Is One Way Slab?

One way slab is a slab that is supported by beams on the two opposite sides to carry the load in one direction. In one way slab, the ratio of longer span (l) to shorter span (b) is equal or greater than 2, i.e Longer span (l)/Shorter span (b) ≥ 2

One Way Slab Reinforcement Details

In one way slab, as one side is larger than the other one, the maximum load will be conveyed by the larger side. Therefore it is important to provide adequate support to this side.

To provide adequate support to the longer side, the main reinforcement bars are provided parallelly to the shorter side and the distribution bars are provided on the longer side which won’t help in carrying the load.

In the above slab, Larger span/Shorter span = Lx/Ly = 4500/2000 = 2.5>2

So it is a one-way slab. In this slab, the main reinforcement bars are provided on the shorter side and distribution bars are provided on the longer side.

What Is Two Way Slab?

When a reinforced concrete slab is supported by beams on all four sides and the loads are carried by the supports along with both directions, it is known as the two-way slab. In two way slab, the ratio of longer span (l) to shorter span (b) is less than 2.

i.e Longer span (l)/Shorter span (b) < 2

These types of slabs are mostly used on the floor of multi-story buildings.

Two Way Slab Reinforcement Details

In two way slab, as the loads are carried in both directions (longer and shorter direction) main reinforcement bars are provided in both directions. The loads are carried by two sides are equal. Slab with reinforcement in both directions is more economical than one-way reinforcement slabs.