A flat plate floor system is a reinforced concrete frame system with a uniform thickness that is supported directly over the columns or the load-bearing walls. The flat plate floor system is a common floor construction type employed in the construction of the building.

The important features, construction and the advantages of employing a flat plate floor system are briefly explained in this article.

## Features of Flat Plate Floor System

The important features of the flat plate floor system are enlisted below:

- One of the important features of a flat plate floor system is the thickness of the floor. It is constructed with uniform thickness with a flat soffit.
- The soffit constructed for a flat plate system requires simple formwork which hence makes the construction easier.
- The flat plate floor system is the best choice for serving the purpose of a horizontal floor over a suspended ceiling.
- The flat plate floor is constructed with an economical span that takes up medium loads and avoids the chances of long-term deflection.
- A flat plate floor system depending upon the load and deflection criteria can be either pre-cambered or prestressed.

## Construction Details of Flat Plate Floor System

A flat plate floor can be constructed with an economical span of 6 to 8m for ordinary reinforced flat plate floor. For prestressed construction, the economical span can be increased to 8 to 12m.

In general, if D is the depth of the slab, then

Span ‘L’ for a Simply Supported Reinforced Concrete Flat Plate System = D x 28

Span ‘L’ for an End Span Continuous Reinforced Concrete Flat Plate System = D x 30

Span ‘L’ for an Internal Continuous spanned Reinforced Concrete Flat Plate System = D x 32

If the flat plate system is prestressed, the span L can change to D x 30, Dx 37 and D x 40 respectively.

## Advantages of a Flat Plate Floor System

The basic advantages of a flat plate floor system are:

- A flat plate floor system does not demand any beam.
- The use of zero beams helps to have underfloor spaces and more service areas.
- The flat plate floor system requires simple formwork. This system is suitable for a direct fix or sprayed ceiling.
- The structural depth of a flat plate floor is minimum.
- Reduced depth of slab helps to increase the floor to floor height of the building.

## Disadvantages of Flat Plate Floor System

The basic disadvantages of a flat plate floor system are:

- The lateral load capacity of a flat plate floor system is limited compared to a moment frame.
- The spans employed are medium length
- Special reinforcement for shear must be provided at the columns or larger columns must be constructed.
- Long-term deflection is an expected factor that requires full life control.
- A flat plate floor system is not a good choice for supporting partitions that are too brittle. For example Masonry Walls.
- A flat plate floor system is not a good choice to take up heavy loads.

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