Stair Design: Introduction
Stairs, along with ramps, remain the primary means of vertical movement, both inside and outside buildings, and are one of the key elements of architectural composition. The definition of a staircase is very simple: a series of treads and risers; but since ancient times, we have adapted them to serve all kinds of purposes—there are triangular ones, scissor-type ones, straight ones, helical ones, tiered ones, mechanical ones, and ramp-style ones.
Furthermore, we have imbued them with all kinds of meanings. Rocky It wouldn't be the same without that memorable scene on the steps of the Philadelphia Museum of Art, where a podium crowns the champion on the top step. But what prompts us to write this article today is the strictly functional aspect of a staircase, which is that of to take us from height “x” to height “y” in the most comfortable and safe way possible.
It is clear that we can simplify stair calculations and design to the mere execution and compliance with the Golden rule: The sum of two risers and one tread must be between 63 and 65 centimeters. But it is up to the architect or engineer’s professionalism and skill to know when and in what situations to use that range between 63 and 65 centimeters, since we won’t always have the same conditions in every project.
We should apply this ratio to low-traffic staircases, since these types of staircases are quite steep and should be used when there isn’t much available length for the staircase. We must also ensure strict compliance with the legal requirements for use as an emergency escape route, since the short tread length makes descending the staircase risky.
18 cm tread and 28 cm riser = 64 cm
This is the optimal ratio for a staircase, allowing for the smoothest and safest ascent. For this reason, this ratio should be used whenever possible, and in the case of public staircases that are part of an emergency exit route, it is mandated by regulation. Regulations may vary slightly from country to country, but if these dimensions are not specified, the actual dimensions will be very close to them.
13 cm tread and 39 cm riser = 65 cm
Clearly, this is a more spacious path that runs closer to horizontal, and it is only recommended for outdoor areas or very wide staircases designed for architectural purposes. Since the spacing between the steps doesn’t actually make it very comfortable, let alone the safest option.
Is this enough to design a staircase?
The answer is no. A staircase involves other factors that must be considered and that are vital to ensuring the building’s accessibility and safety. The most important ones to keep in mind are:
- The width of the staircase: They are typically established by each country’s technical accessibility regulations, but in general, public spaces are required to have a minimum width of 1.20 meters which allows two people to pass through at the same time. Narrower widths can be designed for private and residential spaces.
- Breaks: They are generally specified at intervals of 10 to 12 steps, but should definitely not exceed 15, and their length must be equal to or greater than the width of the staircase or a minimum of three treads combined.
- Staircase shape: As we mentioned earlier, there is no set way to design a staircase; they can be “spiral,” triangular, “scissor,” helical, or “L”-shaped; the important thing is to maintain proportions that ensure proper functionality and comply with local technical regulations. In these cases, we recommend consulting Ernst Neufert’s *The Art of Architectural Design*.
- Ventilation: This is an important consideration in the main circulation cores of multi-story buildings, which must be designed to prevent smoke from entering in the event of a fire while ensuring ventilation throughout the entire core; to this end, specialized mechanical ventilation systems must be provided.
As you can see, there are many factors to consider in the stairway design, which will determine which is the best option for each project.
