Oh, then I am too narrow inside with the walls, I had read that most construction companies work with 15 cm for load-bearing walls or 12 cm for partition walls.
Yes, it varies. Inside, often less is sufficient. But also think about soundproofing. The thinner, the more permeable to sound. Each wall must be considered individually regarding [statics] and [sound].
Our architect or structural engineer can gladly do that [emoji846], but since we are talking about measurements, can someone tell me the approximate common width of a front door with a narrow side panel?