297space-containing wall contains chambers, niches or small an-
cillary rooms, which not only appear as > porosity, but also
transform the wall into a space. Besides being the boundary
of a space, it can itself be fashioned into a cavity through hol-
lowing out, > layering or > folding, rendering spatial bounda-
ries soft or indistinct, or staggering them into > depth. The
spectrum extends from the plastic modelling of a wall relief
with small niches all the way to the recesses of a multilayered
wall that contains loggias, bay windows, > galleries or > ar-
cades. In the simplest instance, an interval between two wall
layers is formed by doubling. Either side of the double wall
can be more or less perforated or dissolved, thereby opening
itself up in various ways to adjacent spaces. Through the var-
ying shaping of the contour on both sides, the hollow spaces
too alters its form.
Because the space-containing shell also has its own
mass and volume (Rudolf Schwarz refers to it as a ‘crust’), it
is simultaneously wall masses and wall space (> space-body
continuum). In addition to space-containing walls, other
structural elements such as supports or ceilings maybe also
regarded as space-containing, provided they offer usable or
accessible cavities.
The cavities of space-containing structural elements rep-
resent a further type of space that lies between interior and
exterior, and generally has the character of an > intermediate
space. It belongs simultaneously to the inside and the outside,
but forms neither a flowing spatial transition nor a division;
it has a complementary function for both sides. Towards the
outside, the space-containing wall mediates between the inte-
rior of the building and the outer space of the city (> facade),
establishing formal transitions, and offering spaces that lie
half-inside, half-outside. For the interior, it is generally as-
signed to a ‘servant’ spatial zone of a principal room, which
it ‘serves’ from the periphery. This hierarchical relationship
between ‘servant and served spaces’ is well known as a char-
acteristic of the architecture of Louis I. Kahn. In this position,