What is a helical staircase?
A helical staircase takes its name from its similarity to a helix: it typically follows a circular path and revolves around a central axis that is empty or is occupied by other non-structural elements of the staircase – this is the main difference from a spiral staircase (the steps of which are anchored to a central post).
Its dimensions, configuration, and materials can vary widely. The cross-section of a helical staircase can be round, oval, elliptical, or curved.
What factors should be considered when designing a helical staircase?
The three main things that must be known to design a helical staircase are:
- The height of the ladder.
- The angle of rotation.
- The total diameter of the staircase’s floor space.
From there, the following formula should be applied to find the perimeter (i.e. the total length of the ladder):
This result divided by the vertical distance that the ladder must cover gives the total number of stairs, as well as its size. The useful line – the space through which the user moves — should be located ⅔ from the center.
What are the main advantages of a helical staircase?
Compared to conventional stairs, helical structures offer space saving in planning and building staircases. However, this is not the most economical structure. Spiral staircases need less space, but they also present other problems: they are less comfortable and safe, and they can be less aesthetically interesting.
Helical staircases have significant aesthetic potential, so they are often used not only as a utilitarian element but as a feature that is characteristic of structural designs.
In addition, the range of possibilities in its configuration lets it function as a comfortable, safe staircase that is suitable for both restricted areas (a limited number of people in a private space) as well as the public sphere (high foot traffic).
What famous helical staircases are there?
There are at least two famous helical staircases:
The Initiation Well or Inverted Tower of Sintra
This is an underground structure measuring 27 meters deep located in Quinta da Regaleira in Sintra (a few kilometers from Lisbon, Portugal). It has 9 floors (which correspond to the nine circles of Hell in Dante’s Divine Comedy), separated by stairs with 15 steps each.
The Initiation Well is full of mysteries, but we do know that it was intended to be used in masonic rites of initiation. Aspirants traveled through a series of unlit underground tunnels to reach the bottom of the well; in its center is a compass rose on a Templar cross. Then, they had to ascend the tower’s helical staircase until emerging in the gardens, symbolizing rebirth.
The Bramante Staircase in the Vatican Museums
This is a three-level continuous helical structure designed by Donato Bramante, commissioned by Pope Julius II. Its construction began in 1507, and it was completed many years after the death of the architect (who died 7 years after construction began). This structure is technically not a staircase because Bramante designed it without steps.
Each of its turns has 8 columns of different orders (Doric, Ionic, and Corinthian), changing floor by floor. As you ascend, the columns get taller and narrower, drawing on the helical effect to create a dynamic perspective of ascent. Symbolically, this represents the idea of divine connection.
The Bramante Staircase is often confused with the modern double spiral staircase by Giuseppe Momo, built in 1932, which was inspired by the work of Bramante. This structure does have steps, though they are almost imperceptible. While the Bramante staircase — which has been used by some of the most important and influential artists and personalities in the history of humanity for centuries — is restricted access only and difficult to visit, the Momo staircase is currently part of the route in the Vatican Museums and is used by hundreds of visitors daily.