What is the difference between one way and two way slab?

“What is the difference between one-way slab and two-way slabs?” This is a very basic question for every civil engineer at their beginning stage of civil engineering.

Every engineering design needs to follow some basic rules for the completion of most conservative and efficient designs. Load transferring mechanism is one of the key features that should have a high attention in designing even a simple structural element. Even the slab is divided as based on this load transferring assumption when designing.

Load transferring mechanism is how the loads on the structure from humans, furniture and other building occupants are transferred to the foundation level and to the soil to bear the structure in the stabilize form.

The slabs that are support on its all four edges are basically divided as one way and two way slabs based on this load path.   If the loads can be distributed to all four edges of the slab it is two way spanning slab. But even if the slabs are supported on all four edges and a huge fraction of the total load can be transferred mainly in one direction, that slab can be assumed as one way spanning slab.

The basic thump rule says, if the aspect ratio between the length and the width is greater than two, the slab could be assumed as a one-way slab for the simplification in the further calculations.

Generally, the slabs are supported on its all four edges by beams. So it is bit confusing whether the load can be transferred in all four direction as the supports can carry the loads from the slab in any direction. Yes, it’s true. Actually in reality this can happen. But the real ratio of the amount of load transferring in the less dimension direction is comparably less. So that we can simply assume that is one way spanning slab. So, the above thumb rule can be applicable in designing for an easy estimation rather doing complicated calculations.