Winder staircases: what they are and the rules that govern them

A winder is a tapered tread, wider at one end than the other, that turns a staircase through a corner without a flat landing. A common quarter-turn stair uses a set of winders to sweep round 90 degrees. They are a neat way to turn in a tight footprint, but they are also where a lot of stairs quietly fail the rules, because the geometry has to be right and a plan rarely shows it.

Here is what a winder actually has to do to be legal, and the choices around it.

The two rules every winder has to keep

A tapered tread is naturally deeper at the wide end and shallower at the narrow end, so the rules pin down two points:

• The going at the walk line must be at least the going of the straight treads. The walk line is the path you actually tread, taken along the centre of the flight on a stair under a metre wide. Measured there, a winder has to be as deep as a normal step. Get that right and the turn walks like the rest of the stair.
• The going at the narrow end must be at least 50mm. The treads cannot taper away to a point at the newel. That 50mm minimum is what stops the inside of the turn becoming a set of useless slivers you cannot put a foot on.

Hold both of those at once and the winder is sound. Miss either and it is not a tight fit, it is non-compliant.

Two, three or four winders

The number of winders is how many tapered treads share the turn. A quarter-turn is most often made with three winders, which is the classic arrangement and the one most makers build without fuss.

Four winders is not simply three plus one. It is a different, harder turn. Getting four tapered treads around a corner while each one still keeps its full going along the walk line and its 50mm at the narrow end takes noticeably more room, set out as a proper winder box with space allowed going into and out of the turn. It is awkward enough that a lot of manufacturers do not offer four-step winders at all. So if a design leans on four winders in a tight corner, two things are worth checking early: whether it can be built to the rules at all, and whether you can find a maker who will make it.

Winders or a landing?

People often assume winders versus a flat landing is a style choice. Frequently it is not. A landing needs full headroom over it, and in a tight stairwell or a loft there is sometimes simply not the height to put a landing in, which forces winders instead. A landing also resets a flight, so it can be the answer where the run would otherwise be too long. Which one you can use is decided by the real space and the headroom, not by preference, and that is one more thing only a proper measure settles.

Why a winder turn needs room, and why it gets measured

Because the going has to hold up at the walk line while the narrow end stays at least 50mm, a winder turn needs enough width to lay the treads out properly. Squeeze the corner into too little space and there is no arrangement that keeps both rules, so the turn cannot be built legally however neat it looks on the drawing. Exactly how the treads are set out is a craft job, not a number off a form, which is why we set winders out against the real opening rather than trusting a plan. If your stair turns a corner, that is the part worth getting looked at first.

The figures that sit behind this differ across England, Wales, Scotland and Northern Ireland. For the full set, see our guide to UK staircase building regulations, and for how a good plan still hides this, see why a staircase that works on the plan can fail in reality.