🏗 Cantilever Slab Designer

Preliminary design/checking tool • IS 456:2000 + IS 875 (Part 1 & Part 2)

1. Inputs

Cantilever length L (m)

Slab width / design strip (m)

Support beam?

Concrete

Steel

Floor finish (kN/m²)

Imposed load (kN/m²)

Parapet / wall line load (kN/m)

Edge/concentrated load (kN)

Clear cover (mm)

2. Results

Enter the inputs and press Calculate.

Design notes

Design is based on a 1 m strip (scaled to entered width for total actions).
For residential balconies, IS 875 Part 2 Table 1 gives 3.0 kN/m² UDL and 1.5 kN per metre run concentrated at the outer edge; the app separately allows an edge point load.
IS 456 span/depth, flexural strength, shear, detailing and minimum reinforcement provisions are applied in a simplified preliminary design workflow.
“Maximum cantilever” is not a single code-defined number. Actual allowable length depends on geometry, loads, support restraint, deflection, cracking, durability and detailing. This app checks the entered length rather than declaring a universal code maximum.
Not suitable as the sole basis for construction. A qualified structural engineer should verify the final design and drawings.

About the Cantilever Slab Designer

The Cantilever Slab Designer designs balcony and sunshade slabs as per IS 456:2000 with loads from IS 875 (Parts 1 and 2). It works on a 1 m design strip and gives the slab thickness, steel and checks in one sheet.

Inputs

Cantilever length and slab width, with or without a support beam
Concrete grade (M20–M30) and steel (Fe 415 / Fe 500)
Floor finish, imposed load, parapet or wall line load, and an edge point load
Clear cover

Results

Design bending moment and shear at the support
Main (top) steel and distribution steel with spacing
Span/depth deflection check, shear check and minimum steel
Detailing notes, including anchorage of the top bars into the support

For residential balconies IS 875 Part 2 gives 3.0 kN/m² imposed load and a 1.5 kN per metre line load at the free edge. This is a preliminary design and checking tool; get final designs checked by a qualified engineer. Related: minimum reinforcement as per IS 456.

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