Video: Stair Constructions
Every day, any of us repeatedly have to go down and up stairs. A staircase is a construction so familiar to every person that few people think about how, in fact, a staircase is arranged. Meanwhile, a staircase is an integral part of a human home, which must be built according to certain rules and proportions.
Knowledge and understanding of these rules is especially important in cases where there is a need to independently manufacture stairs in a residential or utility room, for example, in a country house. You can build different classifications of types of stairs according to design features or materials used. However, in our case, it is reasonable to divide the stairs according to their functional purpose, which may be as follows:
1. Staircase leading from one level of the dwelling to another (interlevel staircase);
2. A staircase leading to a non-residential premises, for example, to a basement or to an attic (such a staircase can simply be attached);
3. Staircase on the street in front of the house entrance - outdoor staircase.
Historically, two main types of staircase structures have developed - straight and spiral staircases. You can even designate the oldest prototypes of such structures - a series of steps arranged in the hillside, which cause the rise in a straight line (straight staircase), and tree branches, which imply a spiral rise (spiral staircase). Between these extreme types of stairs, the intermediate and most common type of turning staircase should also be designated.
Figure: 1. Spiral staircase
In fact, ascent in a straight line is the most convenient and requires the least physical effort, but at the same time, a single-flight staircase, even in one flight, takes up quite a lot of usable area. A spiral staircase requires a much smaller area, but at the same time has some drawbacks in terms of movement along it (see Fig. 1). This is due to the fact that each step of such a staircase has an unequal width in plan, which increases with distance from the center. Such steps are called winder steps. The optimal path for climbing a spiral staircase is the path in the center of the steps.
The continuous row of steps of the march of the turning staircase provides a straight path for ascent, while the flights themselves are located at an angle (90 or 180 degrees) to each other, which leads to a decrease in the total area occupied by the stairs.
You can be convinced from your own experience that climbing a flight of stairs, which has more than 10 steps, is not very convenient. Therefore, it is customary to equip stairs with intermediate platforms. Such sites, firstly, provide a little rest during the ascent and, secondly, allow you to set the next march in a different direction. The disadvantages of a rotary double-flight staircase include the inconvenience of transporting bulky items (for example, furniture) along such a staircase.
Figure: 2. Quarter-turn staircase
In practice, in order to provide the most acceptable in all respects ascent from one level (floor) to another, a staircase with two flights is sufficient. The second (upper) flight can be located at right angles to the first, in this case the staircase is called a quarter-turn (see Fig. 2), or at an angle of 180 degrees - a semi-turn staircase (see Fig. 3). If the two upper flights of stairs diverge from the intermediate platform in different directions, the staircase is called swinging. A staircase that has more than two flights is called a multi-flight staircase.
Figure: 3. Semi-turn ladder
In addition, it is possible to distinguish an intermediate type of stairs between the rotary and spiral structures (see Fig. 4). Its peculiarity lies in the fact that instead of an intermediate platform, a segment of a spiral staircase with winder steps is performed. In the direction of turning between flights, right (clockwise movement) and left (counterclockwise movement) stairs are distinguished.
Figure: 4. Intermediate type of stairs
There are certain standards that must be adhered to during the construction and installation of stairs. There must be a distance of at least 2 meters vertically between two flights or between the flight and the ceiling to ensure free movement of an adult. The width of the march should allow for the simultaneous movement of two people up the stairs and in any case cannot be less than 600 mm.
A reliable fence is also an integral part of most stairs. Fences are arranged in the form of handrails with a height of at least 900 mm, capable of withstanding the corresponding loads.
Now that we have got acquainted with the basic principles of staircase construction, we can take a closer look at the construction of a staircase.
Each step of the staircase consists of two elements - a tread and a riser. Their size and ratio determine the proportions and, to a certain extent, the slope of the stairs. Practical experience shows that in order to create optimal conditions for moving up the stairs, one should be guided primarily by considerations of the convenience of this movement.
The main parameter for choosing the ratio of the tread width to the riser height is the width of the human stride. Each subsequent step up the stairs must be equal to the previous one. Indeed, it is enough just to imagine descending or climbing stairs with steps of different heights, as all the advantages of a structure with constant and correct proportions become obvious.
Figure: 5. Ladder construction
1 - tread;
2 - riser;
b - tread width;
h - riser height
The width of the tread (b) is the horizontal distance between the leading edges of two adjacent lower and higher steps of the staircase. The height of the riser (h) is the vertical distance between the planes of the treads of adjacent steps of the staircase (see Fig. 5). The basic rule for obtaining the required proportion of the step can be formulated as follows: the doubled sum of the riser height and tread width should be 600–650 mm. For example, if the riser height is 160 mm, then the tread width should be 280–330 mm.
However, not all sizes that formally fit into the above equation can be applied in practice. For example, a step with a riser 90 mm high and a tread width of 470 mm meets only the specified requirements, but not the convenience of moving up the stairs. Therefore, the height of the riser has certain dimensions that can vary from 140 to 170 mm, with extremely permissible values of 120 and 200 mm. In practice, the tread width is taken to be 280–300 mm, but not less than 250 mm. Usually, the real width of the tread is even slightly increased in relation to the calculated one (by about 20 mm).
To determine the height of the riser, first of all, you should measure the distance between the floors to be connected by the stairs. This can be done according to the drawing, but it is better directly in place, since the real height sometimes differs somewhat from the calculated one. If the height of the riser is chosen in advance, a situation may arise in which the number of steps on the stairs will not be whole. Therefore, it is more correct to divide the height of the staircase into an integer number of steps, to obtain the required riser height as a result and to calculate the appropriate tread width accordingly.
In this case, two more regularities should be taken into account to build an optimal step size. The most convenient are stairs with a tread to riser ratio b - h = 120 mm. This equation is called the "convenience formula". At the same time, for the safest movement, it is more reliable than a structure with a ratio b + h = 460 mm (the so-called "safety formula").
It should also be borne in mind that the width of the tread should provide the ability to fully and reliably support the entire surface of the foot on it. If the tread is too narrow, the foot may slip off the tread as you move down. If the tread, on the contrary, is too wide, then when moving up the leg, as a rule, does not rest on the middle of the entire foot.
The tread to riser ratio determines the slope of the staircase. There are gentle stairs (slope up to 38 degrees) and steep (slope from 38 to 45 degrees). If the width of the tread is equal to the height of the riser, then the staircase has a slope of 45 degrees, which is the limit for residential premises. Indoor staircases typically have a 38 degree slope. At the same time, stairs to utility rooms (for example, to the attic) can have a slope of more than 45 degrees. In such cases, they are usually made attached. The most suitable riser to tread ratio for residential use is 1: 2 (eg 150: 300 mm).
The number of steps in a flight of stairs can be from 3 to 18 (although a flight with more than 10 steps is not very convenient), while it is desirable that their number be odd. The structural basis for the steps is usually two inclined beams. In the case when they are located below, and the steps rest on them, the beams are called kosoura. If the beams are located on the sides, and the steps are cut into them or reinforced with thorns, the beams are called bowstrings.
Materials for making stairs
A wide variety of building materials can be used for the manufacture of stairs. Their choice depends both on the functional purpose of the stairs and on their location. For the execution of outdoor stairs, durable materials that are not afraid of moisture and temperature changes are more suitable - brick, metal or concrete. The wood used for the manufacture of outdoor stairs requires additional treatment with antiseptics.
In addition, it is necessary to take into account the possibility of icing on the steps in winter. To increase the safety of such stairs, the tread surfaces should be corrugated. External staircases made of brick or concrete can be additionally clad with various finishing materials. For this, stone (granite or marble) or tile (including mosaic) tiles are used.
Internal stairs are usually made of wood or metal. It should be noted here that the manufacture of a metal structure requires special equipment and, in terms of complexity and labor intensity, is an order of magnitude superior to similar structures made of wood. At the same time, metal ladders are much stronger and more reliable than wooden ones, and in any case they are safer in terms of fire safety.
In the manufacture of wooden stairs, oak and pine wood is most often used (other conifers are also used - cedar or larch). Oak has a higher density and, accordingly, is more reliable in use. Conifers are noticeably softer than oak, but more convenient in processing. The humidity of the wood used for the manufacture of the stairs must correspond to the humidity of the room in which it will be located. The existing variety of ladder designs allows using both wood and metal for their manufacture.
We reviewed the main design features and proportions of the stairs. In the future, a more detailed description of the technology for performing straight and rotary, spiral, attached and external stairs will be given.
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