Spiral stairs and helical stairs

Spiral and helical staircases can create a sense of light within properties, they can take up less space than traditional stairs, and can create a focal point to a design. They are often available as pre-fabricated kits.

Approved document K, Protection from falling, collision and impact, gives the following definitions.

• A spiral stair is a stair in a helix around a central column.
• A helical stair is a stair in a helix around a central void.

The approved document requires that spiral stairs and helical stairs are designed in accordance with BS 5395-2 Stairs, ladders and walkways. Code of practice for the design of helical and spiral stairs [1984 + AMD 6076, Corrigenda July 2008, C2, C3]. It gives recommendations for the design of internal and external helical and spiral stairs and gives guidance on the geometry of helical and spiral stairs, including:

• Alternative materials, components and methods of design and construction.
• Materials.
• Design.
• Fire protection and means of escape.
• Load tests.
• Design geometry.
• Typical layouts for stairs.
• Relationship between rise and going.
• Measurement of clear width and goings.
• Landings.
• Maximum gap between column and tread.
• Calculation of going.
• Calculation of clear headroom.
• Structural materials.
• Sizes of stairs.

Helical and spiral stairs involve the use of tapered treads. A tapered tread is a step in which the going (the depth from front to back of a tread, less any overlap with the next tread above) reduces from one side to the other. Approved document K requires that consecutive tapered treads, should use the same going. If a stair consists of straight and tapered treads, the going of the tapered treads should not be less than the going of the straight treads.

[edit] Related articles on Designing Buildings

• Approved Document K.
• Building regulations.
• Escalator.
• Inclusive design.
• Lifts.
• Railings.
• Spiral staircases for homes.
• Spiral staircase kit.
• Stairs.
• Stairs going.
• Stairs nosing.
• Stairs riser.
• Stairs tread.
• Types of stairs.