First, lighting, such a small area, lighting will certainly be affected, especially low-rise households.
The second is ventilation. As mentioned above, because the distance between the two floors is too close, the ventilation of some floors will be affected, and the wind will form a crosswind between the two floors and cannot blow into the room.
The third is privacy. If there is no shelter, everything in the house will be seen by the upper-level residents in the adjacent building.
The fourth is security. If you throw something upstairs, it's easy to bump into the glass.
Fifth, the psychological function, the space is so small, and in the face of the above problems, people feel unsafe and depressed.
In short, if possible, try not to choose the house above. However, if it is really restricted by conditions, such as children going to school, then use decoration to change it. Relative to privacy issues, you can hang curtains or stick one-way stickers. In terms of safety, safety barriers can be added.