Stairs (definition and dimensioning)

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The guidelines for the construction of stairs vary depending on the regulations. The requirements for the dimensions of the stairs are defined by standards. For apartment buildings with two apartments maximum the minimum useful width is 0.90 m and the height / depth ratio of 17/29.

In summary 

1- Definition:
2- Characteristic of a staircase:
3- Terminology of a staircase:
4- The elements to know for the calculation of a staircase:
5- Stairs with straight steps:

  • 5-1- DETERMINATION OF THE NUMBER N OF MARKET HEIGHTS:
  • 5-2- DETERMINATION OF THE HEIGHT OF THE MARKET:
  • 5-3- CALCULATION OF GIRON G:
  • 5-4- CALCULATION OF STAIRCASE RECOVERY:
  • 5-5- CALCULATION OF THE ESCAPE OF A STAIRCASE:

6- Guardrails and ramps:

  • 6-1- GUARDRAIL:
  • 6-2- RAMPS: 

1- Definition:

The staircase is a work consisting of a regular series of horizontal plans ( steps and landings ) allowing, in a construction, to pass on foot from one floor to another, it is also considered to be a work of vertical circulation.

2- Characteristic of a staircase:

A staircase is characterized by:

2. 1- General design of a staircase:

Straight staircase , screw in a turning area , etc.

The French staircase : its steps are carried, on the central day side, by a stringer in which they are embedded and, on the wall side, by a rack.
The English staircase has its steps supported by racks, with one end overhanging the day.
The staircase Italian is inserted staircase (encloses) between two walls.
The attached staircase has its steps embedded at one end in a wall.
The spiral staircase , or spiral, or spiral, has only radiating steps; it is either with central core, or with central day (or light).

2. 2- its composition :

wood, poured or precast concrete, metal, stone, marble or even glass.

2. 3- its steps :

They are square ( straight flights ), dancing or balanced ( stairways with revolving quarters ), or radiant ( spiral staircases ).

2.4- its dimensions:

  • the height of storey H to cross, or height from ground to ground.
  • the bench press, length L of the course of the stride line taken in the middle of the volleys or 50 cm from the ramp.
  • the inclination of the flights : it is 25 to 40 ° for an internal staircase .
  • step height and lap.

Experience proves that a staircase is pleasant if the values ​​of step height (h) and lap (g) correspond to this formula (de Blondel): 2 h + g = 0.64 m Escalators , or stairs rolling , are with mobile steps articulated on an endless chain driven by a motorized mechanism.

3- Terminology of a staircase:

terminology of a staircase

The step : useful width of the staircase , measured between walls or between stringers.
The step height: vertical distance which separates the top of a step from the top of the next step.
The heights of the steps of the interior stairs vary from 17 to 20 cm approximately.
In staircase dimensioning calculations , the height is often designated by
the letter H.
The fold: horizontal distance measured between the noses of two consecutive steps. The treads of the steps of the interior stairs vary from 27 to 32 cm approximately. In staircase design calculations , the lapis often designated by the letter G.
The riser: designates either the vertical face situated between two consecutive steps, or the piece of wood or metal closing the space between these two steps.
The step: flat surface of the staircase on which one steps to go up or down. By extension, the term also designates the piece of
wood or metal that receives the foot. The word “step” is also used to name the assembly formed by the step and the riser, particularly in the case of massive concrete stairs .

There are two main types of steps:

  • The straight step, rectangular in shape.
  • The swinging trapezoidal step.
    On balanced stairs , this type of step allows the change of direction.

The stair nosing: front edge of the step, projecting from the lower riser.
The flight: all the steps of a staircase , between two consecutive landings.
The stride line : fictitious line representing the theoretical trajectory followed by a person taking the stairs.
The staircase or telescope day: central space around which the staircase develops.
The riff or ridge wall: designates the wall on which the steps of a staircase bear . Often called, incorrectly, “walls of échiffre” walls delimiting the cage staircase even when they do not support thestaircase .
The breakaway: clear passage height measured directly above the steps.

There are two types of breakaways :

  • The height measured between two flights of superimposed steps . This distance is usually equal to a ceiling height, approximately 2.50 m.
  • The minimum passage height measured between the step and the edge of the staircase hopper . This distance should not, in principle, be less than 1.90 m.

The drop: total height crossed by a staircase . In the case of an internal staircase , it is equal to the free height under the ceiling increased by the thickness of the arrival floor. The height difference is also called the height to climb or the height of the stairs .
Backing up: length of the staircase projected to the ground. The setback defines the size of the staircase .
The staircase hopper: opening made in a floor allowing the passage of the staircase .
The landing: concrete, wooden or metal platform located at the end of a
flight .

There are several types of bearings (fig. 13.5):

  • The inlet bearing or floor bearing also sometimes called bearing communication:
    bearing located in the extension of a storey floor.
  • The intermediate bearing or bearing rest:
    bearing inserted between two stolen and located between two floors. In principle, an intermediate level
    does not serve any premises.
    This type of landing is made necessary when the number of steps is too large for a single flight or when the second flight is not placed in the extension of the first.
    In this case, it is sometimes called the corner landing or corner landing .

The stairwell: space limited by floors, walls and / or partitions inside which the staircase is placed .

4- The elements to know for the calculation of a staircase:

  • RECOIL: Length of the flight of stairs projected on the ground.
  • HEIGHT TO CROSS: Height crossed by the staircase.
    It is equal to the height under the ceiling + the thickness of the floor.
  • ESCAPE: Minimum passage height should be greater than or equal to 2.00 m.
  • CROWD LINE: This is the theoretical path taken by the user.
staircase: dimensions useful for calculation
  • G = GIRON : Distance between two successive step noses or step width if there is no nosing.
  • H = HEIGHT : Vertical distance between two consecutive steps.
stair nosing

5- Stairs with straight steps:

GENERAL:

These are the most common stairs . They consist of rectangular steps and all identical to each other. See examples

Examples of stairs (straight staircase, spiral staircase ...)

DIMENSIONS OF THE MARKETS:

we will size the steps using the formula below called Blondel relation

  • 60 cm ≤ 2 Heights + 1 Tread ≤ 64 cm

for a common staircase serving the floors of a dwelling, the average values ​​(in cm) of H and G are:

  • 16.5≤ H≤ 17.5
  • 27≤G≤ 31
CALCULATION METHOD:

OBSERVE THE PERSPECTIVE LISTED ON THE OPPOSITE.
The backward movement of the staircase to be calculated cannot exceed 4.20 m (presence of a landing door). The breakaway must be greater than or equal to 2.00 meters.

5-1- DETERMINATION OF THE NUMBER N OF MARKET HEIGHTS:

abacus calculation of stairs
  • at. For a height to be crossed of 2.75 m and a height H of step of 16.5 cm, the abacus indicates:

N = 16.2

  • b. For a height to be crossed of 2.75 m and a height H of step of 17.5 cm, the abacus indicates:

N = 15.6cm

see explanatory diagram below:

Calculation of stairs according to the abacus

5-2- DETERMINATION OF THE HEIGHT OF THE MARKET:

Finally, the values ​​of N found above are rounded up to the next digit. Use of the abacus .

  • a- height to be crossed = 2.75 m N = 17

The abacus indicates : H = 16.2 cm.

  • b- Height to be crossed = 2.75

N = 16
The abacus indicates : H = 17.2 cm

See explanatory diagram below:

Calculation of stairs according to the abacus

5-3- CALCULATION OF GIRON G:

With the formula: 2H + G = 62 cm (average value of the blonde relationship).

  • a – 2 x 16.2 + G = 62 → G = 29.6 cm
  • b – 2 x 17.2 + G = 62 → G = 27.6 cm

5-4- CALCULATION OF STAIRCASE RECOVERY:

No. of GIRONS = No. of HEIGHTS

  • a – 29.6 x16 = 473.6 cm. Solution not retained because:

473.6> 420 (max.

  • b – 27.6 x 15 = 414 cm
MAX RECALLING OF A STAIRCASE

Solution chosen because: 414 <420

5-5- CALCULATION OF THE ESCAPE OF A STAIRCASE:

See figure below.

  • b – 414 – 370 (length. Hopper) = 44 cm. → 27.6 (1 Giron) <44 <55.2 (2 Girons). There are two heights to consider

for the calculation of the breakaway. 250 – (2 x 17.2) = 215.6 cm.
215.6> 200 (mini breakaway).

maximum escapement value

DIMENSIONS RETAINED:
H = 17.2 cm and G = 27.6 cm Recoil = 414 cm. Breakaway = 215.6 cm.

6- Guardrails and ramps:

6-1- GUARDRAIL:

” A guardrail is a work which has the role of protecting against the risks of accidental fall in the vacuum, the people stationing or circulating near this last, but not to prohibit them the forced passage or the voluntary climbing”. (Extract from standard NFP 01-012).

– Protection height H (cm):

Thin railingsThick railing
≤ 2025303540455055/ 60
H (residential building)10097.59592.59085808080
H (other buildings)10097.59592.5908580757

Thickness E to take into account depending on the type of railing:

stair railing
Openwork railings:
stair railing calculation

6-2- RAMPS:

only one protective height: 90 cm.

Openwork ramps:
dimension of the banister of a staircase

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