Tools › User guides › Cantilever Slab Designer
The Cantilever Slab Designer designs balcony and sunshade (chajja) slabs on a 1 m strip to IS 456 with loads from IS 875: slab thickness, top main steel, distribution steel, and the deflection, shear and minimum-steel checks.
Open the Cantilever Slab Designer ›
| Field | What to enter | Typical value | Tip |
|---|---|---|---|
| Cantilever length L (m) | Clear projection from the support face. | 1.0 – 1.5 m (balcony), 0.45 – 0.6 m (chajja) | |
| Slab width / design strip (m) | Width of the slab along the support. | 1.0 | Design is per 1 m strip, scaled for totals. |
| Support beam? | No (slab only) or Yes (support beam). | ||
| Concrete / Steel | M20 – M30; Fe 415 / 500. | M25, Fe 500 | |
| Floor finish (kN/m²) | 1.0 | ||
| Imposed load (kN/m²) | IS 875 Part 2: residential balcony 3.0. | 3.0 | |
| Parapet / wall line load (kN/m) | Railing or parapet at the edge. | 115 mm brick parapet 1 m high ≈ 2.3 | |
| Edge / concentrated load (kN) | Point load at the free edge. | IS 875: 1.5 kN per m run | |
| Clear cover (mm) | 20 |
Press CALCULATE: design moment and shear at the support, required thickness, main (top) steel and distribution steel with spacing, span/depth (deflection) check, shear check, minimum steel and detailing notes — including anchorage of the top bars into the support.
There is no single code maximum; the tool checks the length you enter for deflection, strength and shear.
A cantilever hogs: tension is on the top face, so the main steel goes at the top.