Following are the RCC Slab Design and Detailing guidelines

**Reinforced Concrete Slab Design Guidelines**

**1- Effective span of slab**

Effective span of slab shall be lesser of the two

1- L = clear span + d (effective depth)

2- L = Center to center distance between the support

**2- Depth of slab**

The depth of slab depends on bending moment and deflection criterion. the trail depth can be obtained using

1- Effective depth d= Span /((L/d)_{Basic} x modification factor)

2- For obtaining modification factor, the percentage of steel for slab can be assumed from 0.2 to 0.5%.

3- The effective depth d of two way slabs can also be assumed using cl.24.1,IS 456 provided short span is <3.5 m and loading class is <3.5 KN/m^{2}

Type of support |
Fe-250 |
Fe-415 |

Simply supported | L/35 | L/28 |

Continuous support | L/40 | L/32 |

**Or, the following thumb rules can be used**

1- One way slab d=(L/22) to (L/28).

2- Two way simply supported slab d=(L/20) to (L/30)

3- Two way restrained slab d=(L/30) to (L/32)

**3- Load on slab**

The load on slab comprises of Dead load, floor finish and live load. The loads are calculated per unit area (load/m^{2}).

Dead load = D x 25 kN/m^{2} ( Where D is thickness of slab in m)

Floor finish (Assumed as)= 1 to 2 kN/m^{2}

Live load (Assumed as) = 3 to 5 kN/m^{2} (depending on the occupancy of the building)

**Detailing Requirements of Reinforced Concrete Slab as per IS456: 2000**

**a- Nominal Cover**

For Mild exposure – 20 mm

For Moderate exposure – 30 mm

However, if the diameter of bar do not exceed 12 mm, or cover may be reduced by 5 mm. Thus for main reinforcement up to 12 mm diameter bar and for mild exposure, the nominal cover is 15 mm.

**b- Minimum reinforcement**

The reinforcement in either direction in slab shall not be less than

1- 0.15% of the total cross sectional area for Fe-250 steel.

2- 0.12% of the total cross-sectional area for Fe-415 & Fe-500 steel.

**c- Spacing of bars**

The maximum spacing of bars shall not exceed

1- Main Steel – 3d or 300 mm whichever is smaller

2- Distribution steel –5d or 450 mm whichever is smaller Where, ‘d’ is the effective depth of slab. Note: The minimum clear spacing of bars is not kept less than 75 mm (Preferably 100 mm) though code do not recommend any value.

**d- Maximum diameter of bar**

The maximum diameter of bar in slab, shall not exceed D/8, where D is the total thickness of slab.