perimeter form

The perimeter form describes the dominant outline of a building when seen from above, or in a floor plan. When the building's shape changes from one floor to another, the perimeter form which best describes the prevailing outline is chosen.

The outline is considered across the building's floor levels. A small change at one floor need not be the prevailing shape of the building as a whole.

Roof form describes the upper shape, while perimeter form describes the plan outline. Similar roofs can cover buildings with different plan shapes.