If he is a complex architectural element, that’s the stairs. Its design requires countless calculations so that it is both secure and comfortable to use, that is to say the least restrictive possible for its users. Here are some indications concerning the standards that the staircase should ideally meet.
Staircase: an architectural element that is not produced at random
Any staircase must be able to allow the user to climb the floors comfortably with little effort. For this, it is imperative to respect very specific dimensions. Standards were enacted by Jacques-François Blondel, a French architect (1618-1686) who was Director of the Academy of Architecture, and who theorized a ” calculation formula Staircase which we still use today.
Short overview of the glossary relating to a staircase
The technical vocabulary relating to the staircase is very specific and it is important to know it if you wish to manufacture this architectural element yourself. Its glossary includes, for example:
- The stringer, structure of the staircase,
- The size, importance on the ground,
- The breakaway or height directly above the steps: in most cases this is the height below the ceiling.
- The step or passage width,
- The landing(s) also called platforms,
- The steps (we call stolen the steps that are between two landings), the vertical part of each step being called the riser, knowing that some stairs do not have risers,
- The creeping guardrail,
- The ramp which includes the handrail (part on which the user puts his hand) and the creeping guardrail,
- The hopper, opening in the ceiling where the arrival of the staircase ends
- The trimmer, element of the hopper,
- The scale is the wall on which the staircase rests.
This list is not exhaustive.
Staircase: basic calculation
The universally used formula for creating a staircase takes into account:
- The height of a step: h,
- The pitch, which signifies the useful depth of a step, ie the distance between the nosing and the riser: g.
According to Jacques-François Blondel, the best climbing comfort is that offered by a staircase whose tread is high and the height of a step relatively low, as are more generally the staircases of the old era. On the contrary, the steeper a staircase, the less comfortable it is to climb. This is the case with many contemporary staircases that have a low tread and a higher step height.
To build a staircase, it is also necessary to take into account the space available. This constraint may require varying the form of this architectural element and/or the number of steps. But in any case, it is fundamental to stick to:
- A lap of more or less 30 cm and which should not be less than 23 cm,
- A step height of 21 cm maximum but ideally between 16 and 17 cm.
The length of a step on a step is called the no stride. It is considered to be between 60 and 64 cm, but it can be admitted to a minimum of 57 cm and a maximum of 65 cm, always for the sake of comfort. According to Blondel’s formula, it corresponds to 2 h + 1 g. That is to say that we add 2 step heights to 1 tread. Example for a staircase whose step height is 17 cm and the tread is 24 cm, we therefore obtain (2 x 17) + 24, i.e. a stride pitch of 58 cm. This value is also called the Blondel relation.
Dimensions of a staircase: standards
The staircase must comply with standards and regulations if it is intended for the public, if it is a staircase for fire evacuation or if it is an industrial staircase. In the private sector, standards are not mandatory. But individual buildings intended to be sold or rented must comply with the regulations concerning accessibility for people with disabilities.
However, if you want to have a staircase that is both comfortable and safe, it is better to follow the following recommendations:
- The guardrail must comply with manufacturing standards NF P01-012 and NF P01-013
- The dimensions as we have detailed them previously, namely:
- From 21 to 27 cm for the lap,
- From 17 to 21 cm for the height of each step,
- Respect a passage width of at least 70 cm.
This is a minimum to remember, but the dimensions standard do not stop there, because they also concern the angles, the inclinations or the number of steps, namely:
- Angles of a staircase : between 25 and 42°, i.e. around 32° for a straight staircase,
- Inclination of a staircase : it must be acceptable to limit efforts but also the risk of falls. The recommended inclination is between 30 and 35°. The less inclined the staircase, the less effort the user has to make to climb upstairs.
- Number of steps in a staircase : to calculate it, simply divide the height of the stairs by the desired step height. There are generally 17 steps for a height of 2.80 m or 15 steps for a total height of 3.00 m. Of course, always maintain a comfortable step height. The maximum number of steps must not exceed 18 if we want to avoid the staircase being too constraining.
- Floor area (footprint) of a staircase : it depends on the type of staircase.
- Escape : at least 1.90 to 2 m
- wilting : 0.80 to 1.00 m is desirable to allow two users to pass each other without getting in each other’s way.
The constraints faced by stair manufacturers are truly considerable. We therefore do not launch ourselves into this type of design if we do not have any knowledge in the matter. Admittedly, to simplify the task, it is possible to use a online stairs worksheet. But this may not be enough for all those who only tinker very occasionally.
For reasons of security first of all, from practicality and of comfort then, we cannot recommend highly enough to entrust the conception and his installation to a specialist such as a carpenter. A mason can make a concrete staircase and if you want to install a 100% metal staircase at home, it is possible to have it made by an ironworker. The ideal is to ask for several staircase quotes in order to be able to study the different services and compare the prices.