The shape of an outdoor space suggests the kind of function it supports better, lingering or walking. That seems rather obvious, right? A space roughly as long as wide suggests a place for lingering, while a long narrow space urges walking.
However, too often the spaces around buildings or hedges are neither fish nor fowl. They are too wide to be thought of as paths, but they are elongated or go around a corner so they lack the obvious, comforting enclosure of a sitting space. These mongrel places are called negative spaces.
They form no recognizable shape. Their open ends or hidden corners make us restless, so we tend keep walking through negative spaces even though they are uncomfortably wide to be thought of as paths.
We feel settled only in a place where we can see all of its boundaries. Such a space is called convex. The border is constantly turning in on itself to create a round, rectangular or squarish space. In such a plaza, garden, lawn, outdoor room we sense an invitation to linger. If seats are provided, so much the better.
A convex space that is reasonably enclosed is called a positive space. In positive space we feel safer resting, reading, eating, and sleeping where we can see everyone and everything else. So we tend to dwell in rooms and outdoor refuges that are convex.
By contrast, a concave space goes around one or more corners—like an L-shaped room or a curving corridor. Beyond and behind the corner that just into the space, beyond the so-called “casting edge” projected from the viewer past the opaque corner, people and creatures can hide. A concave space is negative space because it prompts at least two sources of restlessness: the worry about what might be hiding around the corner and the forward attraction to discover what might be hiding there.
Thus, the designer’s rule of thumb should be to reshape formless negative spaces by adding other buildings, hedges, or fences to become well-formed paths or positive, convex spaces.