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There may be some confusion between distinguishing spiral and helical staircases. It is understandable because they are highly similar, but each has their own unique feature that makes them differ not only in appearance, but also in function. Let us take a look at each staircase and define their distinct features.
Spiral staircases can be circular/pure spiral stairs, or squared spiral stairs. There are few subtle differences between the two.
As these staircases are very space efficient, spiral stairs give access to different floors while saving floor space, as evident by several famous spiral staircases in the world. They are commonly found in towers and castles because of this reason as functionality is more important for their purpose. There’s also the fact that during medieval times, spiral stairs are wound in a clockwise direction to give defenders an advantage against invading swordsmen as most were right handed, with the newel getting in the way of sword strikes.Spiral staircases have circular stairwells. The steps wind around a newel (or the central pole) to support the steps, with the handrails on the outer side of the circle, while the inner side of the staircase contains the central pole.
While it is valuable when saving space, spiral cases are often steep depending on the diameter of the stairwell. This is why some building codes permit the use of spiral stairs only to remote or small areas in the building.
Old spiral staircases were often made from stone because of the lack of advanced materials at the time. Modern spiral staircases now have the capability to support more weight with better construction, design and materials available in the present. Now, spiral staircases can come in different designs and constructed with different materials for internal and external use.
As the word “helix” implies, helical staircases are designed in a helical shape. Helical staircases differ from spiral staircases as they do not have a newel, and handrails are present on both sides. They are also not limited to a circular staircase, and may be built in an elliptical or oval shape. Without a newel for support, better materials and/or construction is required for helical stairs compared to spiral stairs.
Because of its shape, it is possible to build two helical staircases while occupying the same vertical space, allowing two persons access to a staircase at the same time. Fire escapes are a good example displaying the use of a double helix stair.