With typical brick and concrete structures there are many fixed, nonnegotiable walls and pillars: load-bearing ones that must be present at a precise location a

With typical brick and concrete structures there are many fixed, nonnegotiable walls and pillars: load-bearing ones that must be present at a precise location and aligned with their counterparts on higher and lower floors, or external ones that must respect layout limits (e.g. far enough from the street, leaving a sidewalk of suitable width, global limits of the area of the whole building) and aesthetic considerations (e.g. straight without random recesses, symmetrical repeated units). Flexible internal wall are a minority.