Solid slab are the most common especially in the residential and offices and generally employed when the slab does not exceed 6.0m.

Slab may be solid of uniform thickness or ribbed with ribs running one or two directions. Slab with varying depth are generally not used. Stairs with various support conditions form a special case of sloping slabs.

Slab may be analyzed using the following methods.


a. Idealization into strips or beams spanning one way or a grid with the strips spanning two ways

b. Elastic plate analysis

c. Finite element analysis – the best method for irregularly shaped slabs or slab with non-uniform loads

  • ¬†For the method of design coefficients use is made of the moment and shear coefficient given in the code which have been obtained from yield line analysis.
  • The yield line and Hillerborg strip methods are limit design or collapse loads methods.


Grid floor system is a conventional method of construction in which beams are spaced at a regular intervals in perpendicular directions and monolithic with slab. They are generally employed for architectural reasons for large rooms such as auditoriums, theater halls etc. where column and free space is often the main requirement. A waffle slab is a type of building materials that has two directional reinforcement on the outside of the material giving it to the shape of the pockets on a waffle.

The general provisions for construction and design procedure are given in BS8110: PART 1, Section 3.6.

Slab may be made solid near supports to increase moment and shear resistance and provide flanges for support beams, in edge slabs, solid areas are required to contain the torsion steel.

These type of reinforcement is a common on concrete , wood and metal construction. A waffle slab gives substance significantly more structural stability without using a lot of additional material it makes a waffle slab for large flat areas like foundations or floors. And the floor construction of a dwelling must fulfill several criteria and the following design function must be taken into consideration.

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