Flat Slab Floors

This type of floor is called as beamless slab floor. This flat slab floor is directly supported on columns without any intermediate beams. This type of floor is preferred where heavy loads are anticipated and where there is head room restriction. The columns supporting the floor are invariably circular in cross-section and tops of the column are flared or tapered, which is called as capital. Sometimes certain portion of the slab, symmetrical with the column, is thickened which is called drop panel (Fig. 23.10).

Figure 23.10 Flat slab floor

The flat slab floors have several advantages which are given below:

1. As there is no projection of beam, there is no need for additional ceiling.
2. More clean head room is available.
3. Better ventilation and lighting is available.
4. Even for heavier loads only thin slab thickness is needed.
5. The construction is comparatively easier.

The flat slab floors are preferred under the following conditions:

1. When large equal number of panels are required.
2. Where clear large spans are required.
3. Where there is limitation in head room.
4. The ratio of length to breadth of panels is to be more than 4 : 3.
5. The difference between the length and breadth of any two adjacent panels should not be more than 10% of the greater of the two.

The following two types of systems of reinforcement are in use: (i) two-way system and (ii) four-way system.

In the two-way system of reinforcement, the reinforcement is provided between the columns and perpendicular to the columns. The area left is considered as supported on four sides.

In the four-way system of reinforcement, the reinforcement is placed in four directions. That is two rows of main steel from column to column and other two rows placed diagonally across the panel from column to column.