The Ladder consists of one or several platforms and marches. The march represents a design from a number of the steps connecting among themselves platforms. The top and bottom steps of each march are called frizovymi and differ under the form from the others (fig. 36) a little.
Platforms are divided on floor which arrange at level of a floor of each floor, and intermediate - between floors.
In a march design, except steps, supporting beams and protecting devices in the form of a handrail or baljasnika with a hand-rail enter. The beams supporting steps, name kosourami. When steps only adjoin beams sideways the last name bowstrings. In wooden buildings usually steps and podstupenki cut in a beam (in it do grooves) which also name a bowstring.
Kosoury and bowstrings the ends lean or on ploshchadochnye beams (support platforms), or against staircase walls. Marches can be odnokosournymi and dvuhkosournymi depending on that, how many beams support steps. In the first case of a step one end lean against dredging in a wall, and another - on a beam - kosour.
Ladders happen one - two- and three-mid-flight.
One-mid-flight ladders arrange more often in the one-storeyed buildings highly put over level of the earth; two-mid-flight which take few place and are economic, - in two-storeyed buildings.
If do a two-mid-flight ladder and under a platform provide an exit on street the height between a platform and a ground floor floor should be not less 2100мм.
In building practice the minimum and maximum sizes of elements of ladders are accepted: height of steps - not less 150мм and no more 270-320мм.
Apply steps in the size 150x300мм Is more often that allows suit a march with a bias 1: 2. For garret ladders more abrupt biases are supposed.
In capital buildings the width of the basic ladders should be not less 1200мм, auxiliary - not less 750мм. The width of platforms should be not less than width of marches. Quantity of steps in one march - from 5 to 18.
Correctly to define the sizes of steps, it is necessary to draw a staircase on a sheet of paper in certain scale. We will admit, the project in the two-storeyed house provides a staircase in length 5900мм, width 3000мм and height from level of a floor of the ground floor to level of a floor of the second floor 3300мм. It is necessary to establish quantity of marches and their width, to define quantity of steps taking into account width appear, heights podstupenkov and width of platforms.
For calculation we will designate letters: "р" - width of marches, "с" - a horizontal projection, "т" - width of floor and intermediate platforms, "у" - height of a floor from a floor to a floor, "ф" - an interval between marches, "х"-°шЁшэѕ a staircase, "ц" - length. Having made necessary designations on the drawing, we will start ladder construction (fig. 36, and, see.
36. The device of a wooden ladder :
And - a wooden ladder and its details; - a staircase cut; in - the staircase plan: 1 - frizovaja a step; 2 - a step, podstupenok with prostupju; 3 - podstupenok; 4 - prostup; 5 - a bowstring; 6 - a handrail; 7 - a platform
The Height of a floor from a floor to a floor is equal 3300мм, hence, the ladder owes to the two-mid-flight. Width of a march define under the formula: e-d: 2=1450 at a gleam between marches in 100мм and 1400мм at a gleam 200мм.
The Height of each march will be equal to floor height, delennoj on two, approximately г:2=3300:2=1650мм.
Quantity podstupenkov in each march define division of height of a march into height podstupenka, that is 1650:150=11.
It is considered to be that prostup the top step of each march coincides with a platform surface owing to what the quantity prostupej will be on unit less, that is only 10. Each march will consist from 11 podstupenkov and 10 prostupej. Knowing width appear, equal 300мм, and quantity of steps, it is possible to define a horizontal projection of a march, its length or as it is accepted to name, zalozhenie a march: 6=300X10=3000мм. The width of each platform is provided to equal width of a march - 1450мм.
In that case when in the under construction two-storeyed house the sizes of a staircase are not provided, she can be calculated in such a way. Under the ladder drawing mark platforms, a bowstring and steps. For this purpose on a wall bottom measure width of platforms to 1450мм and from them width of steps or appear to 300мм.
On the received marks spend strictly vertical lines by means of a plumb and namelennogo a cord. Then at ground floor level spend the second horizontal line, from it measure 150мм and spend the second horizontal line, define prostup the first step. Then measure on this line 150мм and from this point spend a horizontal line, defining prostup the second step etc. Last the eleventh prostup should be flush with a platform floor. Thus define position of steps and length of a bowstring.
On the executed breakdown produce a plywood or board template with which help mark a bowstring: find position of beams under a platform and bruska or the logs, stacked on level of a floor of the ground floor. Staircase bowstrings will lean against a beam and brusok. On a design wooden ladders consist of bowstrings, steps and a handrail (baljasnika and protections). As wooden buildings have no more than three floors narrower width of marches - from 1100 to 1400мм there is admissible, and for basement and garret ladders - 800мм is more often.
The Bowstring of wooden ladders usually has a thickness 60-70мм, but if ladders higher the thickness can be 100-120мм. The width of a bowstring depends on the size of steps.
We Will consider the most simple way of connection of steps with a bowstring. On a bowstring cut out grooves or ledges in which krepjat appear and podstupenki. However ledges weaken a bowstring and demand for the device of wider and thick board. Nests for prostupej and podstupenkov can be deaf persons but then a march establish completely collected.
When nests reach the bottom edge of a bowstring, it is better to insert appear and podstupenki from below, after bowstring installation into place. To reduce width of a bowstring, cuts in it lead up not to the bottom edge, and to the top. Having laid steps, from above bowstrings beat brusok with kalevkoj.
Bowstrings of ladders krepjat on beams of ladder platforms differently. It is possible to beat a bowstring to beams skobami or large nails, but such fastening is not so strong. More reliable fastening of a bowstring when in ploshchadochnoj to a beam strengthen a board with cuts into which insert bowstrings with the thorns arranged at end faces. Sometimes a bowstring opirajut on ploshchadochnuju a beam from above, arranging in a bowstring in a place opiranija a corresponding groove. At opiranii beams of ladder platforms on timbered walls it is necessary to take measures to that after deposits of walls of a platform have appeared flush with a wearing floor. For this purpose ploshchadochnye beams opirajut on time racks which krepjat to walls skobami, and under the ends of the beams cut into a wall, leave a backlash equal 1 / 10 of height of a part sruba, located below a platform.
After deposits of walls the put time racks delete and under the ends of beams, that is in nests, put wooden linings of the necessary thickness which fasten to beams. Having strengthened bowstrings and having inserted steps completely or having laid marches, in bowstrings mark places for nests into which insert on thorns of a rack and baljasiny. On baljasiny from above put on hand-rail and fix them.
Ladders collect dry without glue. Them paint oil paints that gives them a beautiful kind and protects wood from rotting. However it is necessary to remember, it is possible what to paint only a seasoned wood. If a material for ladders not quite dry ladders leave for drying for one year and more. To paint them follows in a dry warm season. Some days before colouring a ladder wash and dry.
For movement on svezheokrashennym to ladders stack gangways, boards with filled bruskami. After drying of a paint them remove.