Boundary expansion permitting new level generation

Slight expansion of external boundaries adds useful extra sub-space to the framework. They may be integrated into the framework in such a way as to counteract distortion resulting from the addition of a new level within the framework.

In a sensibly made building every floor is surrounded, at various places, by small alcoves, window-seats, niches, and counters which thus form low-ceilinged "thick walls" around the outside edge of rooms. In a natural building these thick walls, defined by columns, can work as buttresses to counteract horizontal outward thrust generated by the presence of ceilings or higher floors. In order for such an alcove to work as a buttress, its roof must be built as nearly as possible as a continuation of the curve of the floor vault immediately inside.