Slab Design for House: Modern & Efficient Solutions

With the constant development and refining of construction methods and techniques, buildings nowadays are built in a way to withstand harsh weather and offer longevity. The most preferred construction method is following the RCC or Reinforced Concrete Cement structure frame. In this design, the entire weight of the structure is passed onto slabs, beams, and carefully placed columns to let the building stand strongly and equally divide the weight of the structure so not one part has to bear everything. Mentioned in this article is all about the two way slab system and how it helps in construction.

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See also: Concrete slab: Durable and strong foundation for any structure

Two way slab: Definition

Let us start by explaining to you what a ‘slab’ is defined as. A slab is a plain levelled element that helps construction workers to build roofs or floors of a house or building. A slab is built using good-quality reinforced concrete as per the RCC method. Slabs can be constructed in different forms and shapes depending on their use and the conditions. They are also less thick in proportions. Slabs can be one-way or two-way, as per the amount of load they are required to hold while constructing a particular structure.

A two-way slab has bars that run in both directions. These bars carry the weight of the structure equally, thus offering rigidity to the entire floor. The ratio of the long span to short span is less than 2 always in a two-way slab system-

(Prolonged span/ Little span) <2

This slab design is often found in buildings that are either used for commercial purposes or have multiple levels for more firmness and strength. The two-way slab system uses fortifying bars that are placed in a way to help bend it in different directions despite the presence or absence of concrete beams in columned rows. Today the types of two-way slab systems commonly used are slabs with beams, flat slabs and two-way waffle slabs.

Diversion/Deflection of a two-way slab

When constructed to carry the load of a building, the two-way slab is designed in a saucer-like or dish-shaped form. One can lift the corners of the slabs with beams and walls to provide support if the slab is not cast in a monolithic manner. The main beams are made to run through both directions and are laid perpendicularly to each other.

The corners of a two-way slab also need to have additional reinforcement at its edges to not let the slab lift off and create disbalance in the structure. Slabs that are supported by three or two edges are also termed a two-way slab structure. Here, the load of the entire floor gets divided among the ratio of the sides. The two-way slabs are generally 100mm to around 200mm thick, depending on the length of the floor. They work well for panels whose size ranges from 6m x 6m.

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Two way slab: Different design types

The correct two-way slab design to choose for your building depends on many structural, span, length and other constructional factors. Generally, there are three types of two-way slabs generally used in construction.

Two-way slabs with beams

In this first type of two-way slab type, beams are used to provide support to the slabs. The beams and columns can be used and placed at required places which will hold the load of the slabs. This design type is often found in large-scale constructions and even in some smaller structures.

The beams are constructed at the slab’s edge, and the columns get placed along the edges to offer support to both the beam and the two-way slab.

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Two-way waffle slab with beams

The two-way waffle slab design is particularly used in low-rise office buildings and parking lots or found in warehouses and large storage rooms.

This slab design is a two-way support design structure that consists of heavy concrete horizontal structures called joists,  arranged at a perpendicular angle that runs in two directions.  This waffle slab system is used in floor planning structures which usually require a heavy and thick concrete slab due to its weight or widespread length.

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Two-way waffle slabs with integral beams

These types of slab designs are the same as the waffle slabs, but here they use beams for extra support and structure. In large spaces such as an auditorium, where columns cannot be placed for space issues, a waffle slab system works well.

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Two way slab: How to design a two-way slab system?

A two-way slab structure can be built in any preferred way by using correct measurements, methods and materials. To further have correct design analysis, use the DDM(Direct Design method) or the EFM(Equivalent Frame method). The DDM provides regulations to determine the whole design statistics and the equal distribution between positive and negative sections in the moments. Whereas the EFM method uses an equal framework in its structural study to determine both the positive and negative moments that may act in any slab structure. One should also follow the basic rules mentioned in the structural mechanic principles of construction.

Two way slab: What are the pros of using a two-way slab structure?

• A two-way slab design offers more height to any room.

• This design structure allows light to reflect from surfaces, increasing the brightness of the room.

• This clean slab design also increases the aesthetic value of any compound or structure.

• If one prefers a plain flat ceiling, this two-way slab system helps them achieve that with the absence of concrete beams that run through the middle of the cells.

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