Concrete · Special elements
Staircase (waist slab) calculator
Self-weight of steps and waist, bending reinforcement for a flight spanning horizontally, and riser/going checks.
Standard: AS 3600 · NCC riser/going rules
Inputs in the worked example
The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.
| Input | Value | Unit |
|---|---|---|
| Riser | 175 | mm |
| Going | 250 | mm |
| Waist thickness | 170 | mm |
| Horizontal span | 3.6 | m |
| Finishes | 1 | kPa |
| Live load | 3 | kPa |
| Cover | 25 | mm |
| Bar diameter | 12 | mm |
| f'c | 32 | MPa |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Slope θ | 35.0 | ° |
| Self-weight (waist + steps) per plan area | 7.38 | kPa |
| w* = 1.2G + 1.5Q | 14.55 | kPa |
| M* = w*L²/8 | 23.6 | kNm/m |
| Ast | 411 | mm²/m |
| N12 spacing | 270 | mm |
| L/d | 25.9 |
- ✓ 2R + G between 550 and 700 mm (NCC)
- ✓ Riser 115–190 mm
- ✓ Going 240–355 mm
- ✓ L/d ≤ 30 (rough deemed-to-comply guide)
Method, formulas and assumptions
- Waist self-weight per plan area = 25·t/cosθ; steps add 25·R/2
- Flight spans horizontally between landings, simply supported
- Riser/going limits as for NCC stairways (check the NCC for your building class)
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.