Graphical Construction Glossary >> stairs. >> general >> Spiral Stairs

Spiral Stairs
A circular staircase, the treads consisting of winders only. It takes the form of a helix and is quite often called a helical stair.

a spiral stair around a central newel

The stair above is of a type that was and still is built very cheaply and marketed in a manner that may make it attractive. However my personal opinion is that although these stairs may be just the thing for ascending a medieval bell tower (see the previous page), or getting workmen into hard to get at places, they have no place in modern residential design. An architect or designer who uses one of these where a standard flight can be used is not doing his job! Please note these remarks are confined to the small spiral stairs that rotate around a small centre column.

Below is a table for calculating the rise, going and slope requirements for stairs with winders like the stair above. It is detailed in the BCA 2008 edition. It is provided here as a guide for the design of these types of stairs around a central pole and also for what I call helical stairs that have a circular stair well, IE. they have a wider radius.


Spiral stair rise and going dimensions in MM. For stairs up to one metre these measurements refer to sizes taken in the middle of the tread and riser. For stairs wider than one metre then the maximum sizes are measured 400mm from the widest side and the minimum sizes are taken 400mm in from the narrowest side.
a large helical stair
The underside of a wide helical stair out of all steel construction. Seen at Greenwich Observatory, London UK.

As soon as the radius of the spiral increases and with it the width of the stairway then unlike the small and dangerous spiral above, it has the potential to become a thing of beauty.

I prefer the name Helical Stair for this type of stair.

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Please Note! The information on this site is offered as a guide only!  When we are talking about areas where building regulations or safety regulations could exist,the information here could be wrong for your area.  It could be out of date!  Regulations breed faster than rabbits!
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