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How to use the staircase calculator

A concrete stair from steps to bars: what each input means, how the flight load is worked out on plan, and why the landings can govern.

All guides Inputs Result Calc sheet Walk-through Mistakes

1. What the calculator does

The staircase calculator designs a reinforced concrete stair: a dog-leg stair onto landings, a straight flight, a stair cantilevered from a wall or one spanning between stringers. It works out the pitch and the effective span, the load on plan from the steps, the waist and the finishes, and checks bending, shear and span/depth for the flight and the landings, with the detailing rules.

The code routes are SANS 10100-1, Eurocode 2 (EN 1992-1-1) and SANS 51992-1-1 (SA Eurocode, 2023 draft annex). The badge names the clauses: SANS 10100-1 cl. 4.9 staircases, cl. 4.3 bending, shear and span/depth, cl. 4.11 detailing; EN 1992-1-1 6.1, 6.2.2, 7.4.2 and 9.3.

Staircase calculator header with the PASS badge — The header: PASS 96 %, governed by the top steel of the landing across at end 1.

2. The inputs, group by group

Input	What it means	Typical value
Stair	Design code and the stair type: dog-leg, straight, cantilever from a wall, or between stringers.	dog-leg onto landings
Flight	Rise and going per step, number of risers, waist thickness and stair width.	170 / 250, 9 risers, waist 150, 1000 wide
Ends	The support at the bottom and top: a landing spanning across, a beam or wall (monolithic), a simple bearing, or bolted to an existing slab. “Supports and landings” sets them in detail.	landing spanning across, both ends
Loads	Imposed load from SANS 10160-2 for the occupancy, and the finishes on plan.	1.5 and 1.0 kN/m²
Materials	Concrete f_cu and steel f_y.	30 MPa, 450 MPa
Bars	Main bars, distribution bars and top bars at the ends.	Y12 @ 150, Y10 @ 250, Y12 @ 200
Durability	Cover, exposure and fire rating.	45 mm, moderate, 1 h

Staircase inputs: stair, flight, ends, loads, materials, bars and durability — The inputs. The rise and going set the pitch; 2 × rise + going between about 550 and 700 mm is a comfortable step.

3. How to read the result

The section along the flight draws the steps, the waist, the landings, the bottom, top and distribution bars, the loads and the reactions to scale.

Stair section along the flight with bars, loads and reactions — The section: 9 risers of 170 on a 250 going, pitch 34.2°, effective span 3000 mm, M_max 12.4 kNm/m, reactions 15.3 kN.

The design result gives the pitch and the effective span, the flight load on plan (the steps and the sloping waist weigh more than a flat slab), the moment against the resistance, shear, span/depth and the reaction per end, which goes to the landing, beam or wall below.

Design result card for the staircase — Design result: pitch 34.2°, span 3000 mm, flight load 7.39 / 1.50 kN/m² on plan, M 12.4 / 26.0 kNm/m, span/d 30.3 / 42.8, reaction 15.3 kN per end.

The badge names the governing check; here the top steel of the landing at end 1 at 96 %, not the flight. Where the landings carry the flight, they are often what governs. Anything the engine could not run shows as NOT CHECKED.

Design checks summary for the staircase — Design checks: SANS 10100-1 · 31 pass.

4. Calc sheet, drawing and schedule

The result (pass / fail and utilisation) stays free for everyone. Every check with its clause, the calc sheet and the bending schedule are open to signed-in users. Sign in free: 3 designs a month (one calculator, open for 24 hours). Unlimited with a calculator pack.

The bending schedule card reads: “Sign in (free): 3 schedules a month. CSV with a paid plan.” The full reinforcement detail drawing is part of the paid plan.

Reinforcement detail panel marked paid plan — The reinforcement detail drawing is part of the paid plan.

5. A 2-minute walk-through

Open the calculator: a dog-leg stair of 9 risers, 170 / 250, waist 150, onto landings spanning across at both ends.
Read the badge: PASS 96 %, the landing top steel at end 1.
Raise the imposed load for a public stair and see what governs.
Change the type to cantilever from a wall and see the design change.
Change the bottom support to a beam or wall and compare the moments.

6. Common mistakes

The flight load as a flat slab. The waist is sloping and the steps add weight; the engine works this out on plan, so give the waist, not an average thickness.
Landings forgotten. A landing spanning across carries the flight reaction; it can govern, as here.
Imposed load for a home on a public stair. Use the SANS 10160-2 value for the occupancy.
Bars that cannot turn the corner. At the kink between flight and landing the bars must cross, not follow the inside corner.

8. Learn more

Try it nowThe calculator opens with the walk-through inputs above. The result is free; sign in for the checks, calc sheet and schedule.
Open the staircase calculator

A guide to using the calculator, not a design. Check every value against the current code and your own project, and have the design checked and signed by a registered professional engineer.

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