| Primary value | 215 mm (for 1.5 m projection (L / 7)) |
| Applies to | Chajjas (sun shades) · Cantilever balconies without edge beam · Cantilever staircase landings |
| Exceptions | With edge beam (acts as simply-supported) → L / 20 |
| Heavy load (> 5 kN/m²) or finishes → L / 6 | |
| Measured as | L is the projection from the face of support. Effective depth d at the support is overall depth minus cover minus half bar diameter. Cantilevers taper — the slab can thin from root to tip. |
| Source | IS 456 — Clause 23.2.1 ✓ Verified |
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Cantilevers fail at the support — that's where moment is highest. L/7 is the IS 456 deflection limit, far stricter than slab ratios because there's no continuity to relieve deflection. A 1.5 m chajja needs 215 mm effective depth at the root — typically 250 mm overall.
Most residential chajjas are 150–200 mm — only acceptable when the projection is under 1 m. Anything past 1.5 m without a beam edge is a red flag that the structural drawings may be ignoring deflection.