This site will go into detail of if I was to construct a Philadelphia Trinity House. This will fit in a very small space within a lot space of 25′ width. The house will be 15′ × 20′ which is 300sf per floor. With such a small floor plan, the only way to make the space usable is to provide for a Philadelphia Trinity House. The concept is simple. There will be a basement, and either 2 or 3 floors above ground. In this case, it will be 3 floors above ground. Each room will be its own floor. For example, the kitchen (and kitchen only) is the major room of the basement. Only the Living Room will be on the ground floor. I am sure you get the idea.
As with all of the houses I would write about – this house will have spiral stairs, and an elevator. This is to minimize the infrastructural space needed for the house. You can learn about the basics by going to https://fsp.house. This site is very small, but so is the house it represents.