In fact, since childhood to find this problem
Lived in the home, there are relatives and friends of the home, stairs are the number of steps 9 ... does not mean that the building has 9 floors Oh!
For example, from the first floor to the second floor of the stairs is the number of steps 9 ... Of course, this is not all, but I think most of the homes are like this, what is the reason?
1, "Civil Building Design General" norms, residential staircase every step of the height of not more than 175mm. 2, usually the height of the building between 2800mm ~ 3000mm (of course, now refined decoration of the high-end real estate more than). 3, the general level is 100 for the modulus, that is, most of the houses are 2.8m, 2.9m or 3.0m layer high. Then: 1,3m layer, then the need for 3000/175 = 17.14 steps, that is, 18 steps, double stairs step number 9 +9; 2,2.9m layer 2900/175 = 16.57 steps, that is, 17 steps, 9 + 8; 3,2.8 m layer needs 2800/175 = 16 steps, double stairs step number 8 +8. For the 2.9m layer, the total length of the staircase or in accordance with the 9 steps. The higher the size of the stairs, the more difficult to feel the stairs, especially the need to consider the elderly and children's buildings. So since the total length (which involves the area of ??the house, very sensitive) and 18 steps as long, it is better to make 18 steps more conducive to the lives of households and visitors. So the three common residential high school, at least two-thirds of the stairs is 18 steps. In addition, now the requirements of residential increasingly high, 2.8m high house has been less and less. So most of the multi-storey residential building stairs are 18 steps, 9 + 9 layout.
Our school is 13, my family is 7, sorry ah, to help the busy.
Because the majority of our residential buildings are 2.8 meters high, the state of the stairs is a high degree of 13-18CM (the lower limit may not be accurate), comfortable staircase step height is 15CM. In this way, you divide by 2.8 meters by 15cm and get 18 steps. You see the stairs in the stairs, are folded once, so, 18/2 = 9, so you see the stairs are basically nine step.
Upstairs to say the school 13 step, because his school house height of 3.9 meters or so. 7 stepped I have not seen, it is estimated that the height of 4 meters high bar.
