Winder Steps in Steel Staircases: Layout and Tread Angles

What Winder Steps Are and Why They Are Used

Winder steps are treads that are narrower on the inside of the turn and wider on the outside, allowing a staircase to change direction within its own run. They are useful where a landing would take up space the building cannot spare, such as compact flats, shafts, or stairs fitted between two existing floors.

In steel construction, winders must be planned early because the stringers, supports and connections all depend on the tread geometry. A change made late in the process often means re-cutting material or redrawing the whole structure.

Setting Out the Walkline

The walkline is the imaginary path a person follows when climbing, normally about half the way across the tread width. On winder steps it is the reference for measuring the usable tread depth, because the inner end of each wedge is too narrow to step on.

• Mark the inner and outer edges of the stair plan on the drawing.
• Draw the walkline at the agreed distance from the inner edge.
• Confirm that the depth at the walkline matches the design rise and tread values.

Calculating Tread Angles

Tread angles are found by dividing the total turn by the number of winder treads. For a 90 degree turn with three winders, each wedge is typically cut at around 30 degrees, and for a 180 degree turn the same logic applies across the number of treads used. The angles must be checked against the actual plan, since the centre of rotation and the stringer geometry affect the result.

Always verify the calculated angles with a full-size layout before cutting, and keep a written record of the values used for each step.

Checking Tread Depth and Clear Width

Winder treads can look correct on paper and still be uncomfortable to use if the inner depth is too small. Check the depth at the walkline and also at the narrowest point, and make sure the clear width of the stair respects the minimum required by the applicable standard. Where the exact minimum values are needed, confirm them with the engineer rather than relying on memory or rules of thumb.

Fabrication and Connection Details

Once the layout is approved, the wedge treads are cut from plate or fabricated from profiles and then welded to the supporting structure. Consistent cutting is essential, because small errors in each wedge add up across the turn and can make the last step fit badly.

• Cut and check each tread against the full-size template.
• Drill fixing holes after the frame is square.
• Plan the finish, such as hot-dip galvanizing or powder coating, before final assembly.

Installation and Final Checks

On site, the staircase should be fitted to the actual opening, not only to the drawing, because walls and slabs are rarely perfectly aligned. Check each winder for level, rise consistency and tread alignment, and test that the handrail or guard follows the same geometry as the steps. A short walk-through with the client or site engineer helps catch problems before handover.

Frequently asked questions

Can winder steps be built from steel plate?

Yes, winder treads are commonly cut from steel plate or fabricated from profiles and then finished. The material and thickness should be chosen by the engineer based on the loads and the design.

Where is the walkline measured on winder steps?

The walkline is normally set at a distance from the inner edge of the stair, roughly where a person's foot would land. Tread depth for the winder is measured along this line.

Do all winder steps have the same angle?

Not always. The angles are set so that together they make up the full turn, and they can vary depending on the layout and the number of treads used.

Who should confirm the final dimensions?

The project engineer should confirm the final dimensions, tolerances and standard requirements before fabrication begins.

Common mistakes to avoid

The most common error is calculating tread angles without checking the depth at the walkline, which leaves the usable step too narrow. Another frequent problem is cutting the wedges before the full-size layout has been verified against the actual opening.

Our recommendation

Draw the full stair at full size, mark the walkline, and check every tread before cutting so that the turn closes correctly. Keep one template for each winder and confirm the values with the engineer before production starts.

Summary

Winder steps in steel staircases depend on an accurate walkline, correct tread angles that add up to the full turn, and careful fabrication and installation checks.

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