StairGen Pro › U-Shaped Steel Stair with Sawtooth Stringers
Guide & codes
A U-shaped steel stair with sawtooth stringers: two switchback flights in zig-zag tube and a double-width landing. The step layout is that of the bracketed U-shaped steel stair; the difference is the structure, which leaves the stepped profile visible from below.
For a standard calculation, start with the U-shaped steel stair calculator. This variant is for projects that want the look of a sawtooth stringer and need a breakdown of every horizontal and upright for the shop.
When to choose this stair
Choose the sawtooth U-shaped stair when the switchback is on display and you want both flights to read as a series of steps: zigzag stringers, a double-width landing with its own frame and a post. It is common in warehouse mezzanines and in duplexes with the stair in the middle of the floor.
Compared with the U-shaped stair with brackets, the step layout is identical and only the structure changes: two stringers per flight in 50 × 40 mm tube, and no separate brackets. With P = 7 and Q = 8 steps, the landing sits P + 1 risers above the floor: move steps between the flights to raise or lower it.
Calculator parameters
Each dimension carries the letter used in the editor and on the drawings.
- YTotal rise
- default 2,800 mm · 500 to 8,000 mm
- Height from the lower floor to the finished upper floor.
- XTotal run
- default 3,250 mm · 500 to 12,000 mm
- Plan length available for the flight (on turning stairs, the upper flight).
- WStair width
- default 1,000 mm · 500 to 2,500 mm
- Clear width of the flight.
- ELanding depth
- default 1,000 mm · 500 to 3,000 mm
- Depth of the landing in the walking direction.
- ZTread thickness
- default 50 mm · 3 to 120 mm
- Thickness of the tread (board or plate).
- FNosing
- default 50 mm · 0 to 100 mm
- How far each tread overhangs the one below.
- PSteps, lower flight
- default 7 · 1 to 25
- Steps before the turn.
- QSteps, upper flight
- default 8 · 2 to 25
- Steps after the turn, up to the top.
- AStringer depth
- default 50 mm · 30 to 300 mm
- Depth of the stringer tube.
- GStringer width
- default 40 mm · 20 to 300 mm
- Width of the stringer tube.
- TNumber of stringers
- default 2 · 1 to 3
- One centre stringer, two side stringers or three.
How it's calculated
The total rise Y = 2,800 mm over 16 risers gives 175.0 mm per step. On the upper flight, X = 3,250 mm minus the landing depth E = 1,000 mm is shared between Q = 8 steps: a run of 281 mm and a tread depth of 331 mm. Step formula: 631 mm; pitch: 31.9°; verdict: “Comfortable stair”.
Each stringer is split into horizontals and uprights of 50 × 40 mm tube, and the landing has its own frame and two posts. The sheet of each part in the DXF gives its cutting length and quantity.
Result with the default values
Comfort verdict: Comfortable stair.
Complies with IRC / IBC
| Step formula 2R + G | 631 mm | 600 – 660 mm |
| Tread depth | 331 mm | ≥ 280 mm |
| Pitch | 31.9° | 30° – 40° |
| Riser | 175 mm | ≤ 197 mm |
| Going | 281 mm | ≥ 254 mm |
| Clear width | 1,000 mm | ≥ 914 mm |
| Guarding height | 900 mm | ≥ 864 mm |
Steps
| Risers | 16 pcs |
| Riser height | 175 mm |
| Run (going) | 281 mm |
| Tread depth (run + nosing) | 331 mm |
| Open riser gap | 125 mm |
| Pitch | 31.9° |
| Nosing-to-nosing distance | 331 mm |
Structure
| Tread area | 4.969 m² |
Building codes
At the half-turn landing, neither the IRC nor Approved Document K allows the stair to get narrower. As with any sawtooth stringer, the welds between horizontals and uprights must be checked in the structural design.
The calculator checks comfort (2R + G, going and pitch) and the building code of the country you pick in the panel (here, IRC / IBC for a dwelling): only the limits that code sets for riser, going, 2R + G, width, pitch, risers per flight and guarding. It is for guidance only: always confirm the code in force and local rules.
Building codes by country, with sourcesParts with the default values
The DXF (AutoCAD 2007, in millimetres or inches) carries these parts with their shop marks: one dimensioned sheet per part, the general arrangement and the bill of materials with weights.
What's in the DXF- Z1Stringer · horizontalTube 50×40 × 28
- Z2Stringer · uprightTube 50×40 × 2
- Z3Stringer · uprightTube 50×40 × 28
- Z4Stringer · uprightTube 50×40 × 2
- Z5Stringer · horizontalTube 50×40 × 2
- E1Treadt=50 × 15
- M1Landing frameTube 50×40 × 2
- M2Landing frameTube 50×40 × 2
- R1Landingt=50 × 1
- P1PostTube 80×80 × 2
- B1HandrailTube Ø42.4 × 1
- B2BalusterRound bar Ø16 × 15
- B3HandrailTube Ø42.4 × 1
Frequently asked questions
How is it different from the U-shaped steel stair with brackets?
Only in the structure: here each stringer is a zig-zag of tube and the tread bears on its full depth. With the same dimensions, the number of steps, tread depth and riser height are identical.
Can I change the landing depth?
Yes, with parameter E. A shorter landing leaves more length for the steps of the upper flight; the calculator shares them out again and warns you if the tread depth drops below a comfortable size.
What does the bill of materials include?
The horizontals and uprights of each stringer, the treads, the landing frame and deck plate, the posts, the handrail and the balusters, each with its size, quantity, total and estimated weight.