A spiral staircase is a stair in which the treads wind around a central pillar (the newel). It is sometimes called a winding stair or helical stair. It is a space-saving solution used in small dwellings, monumental buildings and industrial locations.
Construction
A spiral staircase consists of three main components:
- Newel post — the vertical central pillar of timber, steel or concrete, to which the treads are fixed
- Treads — triangular or wedge-shaped treads that wind around the newel
- Handrail — follows the outer edge of the spiral
The treads are narrow at the newel side and wider at the outer edge. This creates the characteristic winding movement.
Applications
A spiral staircase is used where there is little space for a straight or L-shaped stair:
- Loft stair — access to attic or loft
- Mezzanine — extra level in a tall room
- Garden room with upper floor — limited footprint
- Industrial stairs — towers, chimneys, plant access
- Heritage buildings — medieval church towers and castles
Dimensions and regulations
UK Building Regulations Part K and other national codes set requirements for domestic stairs:
| Element | Domestic requirement |
|---|---|
| Minimum tread width (at 270 mm from inner edge) | 220 mm |
| Maximum riser | 220 mm |
| Minimum diameter | approx. 1400 mm |
For industrial or secondary stairs different requirements apply. A generous spiral staircase has a diameter of 1800 to 2200 mm.
Pros and cons
Advantages:
- Compact — takes up little floor area
- Decorative — a focal point in the interior
- Suitable for renovations with limited space
Disadvantages:
- Difficult to carry furniture upstairs
- Not suitable as sole escape route in larger dwellings
- Narrow and steep at small diameters
Related terms
- Newel post
- Riser
- Tread
- Landing
- Stringer
Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.