Internal stairs rules:
1- List + sleeper = 40 to 45 cm
2- Slate x Sleeper = 400 to 450 cm
2-3 (list) + sleeper = 60 to 63 cm
The height of the handrail must not be more than 1 m and not less than 0.75 m.
The lowest fire resistance time of materials in the building and the stairs must be taken into consideration to give greater safety coefficients for the building to be designed.
Reinforced concrete, 18 cm thick, resisting 4 hours.
Reinforced concrete, 10 cm thick, withstands two hours.
Reinforced concrete, 7.5 cm thick, withstands an hour.
Reinforced concrete containing gypsum 15 cm thick, resisting 4 hours.
- To download the ladder:
Iron beams covered with 15 cm thick concrete resist 4 hours.
Iron beams covered with 10 cm thick concrete resist 2 hours.
Iron coated steel bars with a thickness of 7.5 cm, resist 1 hour.
Spiral stairs are the most economical stairs in space
The spiral staircase without an axis fixes the ends of its steps inside the wall and holds on top of each other. As for the axis, the outer steps of the steps are fixed on columns bearing on the lower steps or fixed in the wall.
To draw a strip in the spiral staircase the following steps are followed
1- The horizontal circular projection of the ladder is placed over the place where a sector of the peace is intended to be made and the circle is divided into 12 equal sections by connecting the circle diameters and then numbering and at the same time the vertical distance between the ground floor and the first is divided in equal sizes representing the lists and draw horizontal lines parallel to the ground floor and then numbered with the same Previous numbering.
2- Vertical lines fall from the horizontal projection of each number until its other number corresponds to the sector, thus obtaining a curve.
