A flat slab is a two-way reinforced concrete slab that usually does not have beams and girders, and the loads are transferred directly to the supporting concrete columns.
For more detailed definition: Flat Slab Floor System : Definition & Description
Advantages of Flat Slab
Flexibility in room layout.
Reinforcement placement is easier.
As reinforcement detailing of flat slab is simple, it is easier to place
Ease of Framework installation.
Big table framework can be used in flat slab
Building height can be reduced.
Less construction time.
Use of big table framework helps to reduce construction time
Prefabricated welded mesh.
Auto sprinkler is easier.
Disdvantages of Flat Slab
Flat slabs have some disadvantages also. The major disadvantages are given below.
Span length is medium.
In flat plate system, it is not possible to have large span.
Not suitable for supporting brittle (masonry) partitions
Use of drop panels may interfere with larger mechanical ducting
Critical middle strip deflection
In flat slabs, the middle strip deflection may be critical.
Higher slab thickness
Compared to typical reinforced concrete two way slab system, the thickness of flat plat slabs are higher.