Minimum and maximum reinforcement percentages, bar diameters, and spacing rules for all RCC structural members per IS 456. These are mandatory code provisions — violating them invalidates the design.
Slab (one-way & two-way)
| Rule | Value | Clause | Note |
|---|
| Minimum steel (Fe 415) | 0.12% of bD | Cl 26.5.2.1 | b = width, D = total depth |
| Minimum steel (Fe 250) | 0.15% of bD | Cl 26.5.2.1 | |
| Maximum steel | 4% of bD | Cl 26.5.1.1 | Practically ≤2% |
| Minimum bar diameter — main | 8 mm | Practice | 10mm preferred |
| Minimum bar diameter — distribution | 8 mm | Practice | |
| Maximum spacing — main bars | 3d or 300mm (whichever less) | Cl 26.3.3(b) | d = effective depth |
| Maximum spacing — secondary/dist. | 5d or 450mm (whichever less) | Cl 26.3.3(b) | |
| Minimum spacing | Bar dia or 25mm or max agg + 5mm | Cl 26.3.2 | Whichever is greatest |
Beam
| Rule | Value | Clause | Note |
|---|
| Minimum tension steel | 0.85×bd/fy (≈0.2% for Fe415) | Cl 26.5.1.1 | b = width, d = eff depth |
| Maximum tension steel | 4% of bD | Cl 26.5.1.1 | At any section |
| Side face reinforcement | 0.1% of web area per face | Cl 26.5.1.3 | When depth > 750mm |
| Minimum bar diameter — main | 12 mm | Practice | |
| Minimum bars — top & bottom | 2 bars continuous | Cl 26.5.1.2 | Throughout length |
| Stirrup — minimum diameter | 8 mm (6mm for beams ≤ 150mm wide) | Cl 26.5.1.6 | |
| Stirrup — maximum spacing | 0.75d or 300mm | Cl 26.5.1.5 | Whichever is less |
| Stirrup — minimum spacing | 75 mm | Practice | For placing concrete |
Column
| Rule | Value | Clause | Note |
|---|
| Minimum longitudinal steel | 0.8% of Ag | Cl 26.5.3.1 | Ag = gross cross-section |
| Maximum longitudinal steel | 6% of Ag | Cl 26.5.3.1 | 4% at lap locations preferred |
| Minimum number of bars | 4 (rectangular), 6 (circular) | Cl 26.5.3.1 | |
| Minimum bar diameter | 12 mm | Cl 26.5.3.1 | |
| Lateral tie diameter | ≥ ¼ of largest bar or 6mm | Cl 26.5.3.2(c) | Whichever is greater |
| Tie spacing — max | Least of: 300mm, least dimension, 16 × smallest bar | Cl 26.5.3.2(c) | |
| Maximum spacing between bars | 300 mm | Cl 26.5.3.1 | Along periphery |
| Minimum cover | 40 mm (to ties) | Cl 26.4.2.1 | Effective cover ≥ 55mm |
Footing
| Rule | Value | Clause | Note |
|---|
| Minimum steel | 0.12% of bD (Fe 415) | Cl 34.5 | Same as slab |
| Maximum steel | 4% of bD | Practice | |
| Minimum bar diameter | 10 mm | Practice | 12mm preferred |
| Maximum spacing | 3d or 300mm | Cl 26.3.3 | |
| Minimum cover (bottom) | 50 mm (PCC below), 75 mm (no PCC) | Cl 26.4.2.2 | Against ground |
| Minimum depth at edge | 150 mm | Cl 34.1.2 | For isolated footing |
Retaining Wall (cantilever type)
| Rule | Value | Clause | Note |
|---|
| Stem — vertical steel (earth face) | 0.12% of bD (Fe 415) | Cl 32.5 | Main reinforcement |
| Stem — horizontal steel (both faces) | 0.12% of bD per face | Practice | Shrinkage/temperature |
| Base slab — bottom steel (toe) | As designed | | For upward soil pressure |
| Base slab — top steel (heel) | As designed | | For downward earth load |
| Cover — earth face | 50 mm | Cl 26.4.2 | Severe exposure |
Staircase
| Rule | Value | Clause | Note |
|---|
| Minimum steel | 0.12% of bD (Fe 415) | Same as slab | |
| Distribution steel | 0.12% of bD | | Perpendicular to span |
| Minimum bar diameter | 10 mm (main), 8 mm (distribution) | Practice | |
| Cover | 25 mm | Cl 26.4.2 | Mild exposure |
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