4 meters x 10, 5 long 4 and a half floors of stairs are built at the back of the stairs to build a b

Since I can't see the actual location of the stairs in your house, I have a question here: why can't you consider making stairs (steps) to and fro? If you set up stair treads as shown in your picture, I think it would be difficult to walk so many steps in a row when you go up from the rest platform; If it is made to come and go, then the rest platform is in the middle of the staircase.

In this way, it will be easier to go up and down the stairs. Also, if you make a bathroom under the stairs, it will not be affected.

The height is meters, the length is 4 meters, then, if the rest platform is set to the width of meters, the rest (up and down) each has a distance of meters, assuming that the step width of each step is 25 cm, then a total of 24 steps, up and down the rest platform, respectively, are 12 steps, the step height is about 15 cm (may be in the centimeter), this step height is ideal, and you will not feel strenuous when walking up. Access to the bathroom, right next to the stairs; Under the rest platform, you should be able to stand - and at the same time, in order not to feel too oppressed, you can lower the floor of the bathroom a little. This form of toilet is relatively common in rural areas.

Want architectural design? Haha, would you consider charging it?

Can each facing east open the window to let in light?