The interior of all stone walls, and in fact all masonry walls, will
show condensation of moisture over the interior surface, and if they
are plastered directly on the interior the decorations will be ruined
by the collection of so much water. The cause of this condensation is
the same as that which forms sweat on the exterior surface of a glass
of cold water. In order to eliminate this disagreeable feature, all
masonry walls are furred on the interior before the lath and plaster
is applied. The furring makes an air space between the wall and the
plaster, and all dampness is prevented from penetrating to the interior
surface of the plaster. To further increase the damp-proof qualities of
a masonry wall they are sometimes built hollow, as, for example, the
hollow brick wall, or the hollow terra-cotta tile wall. This air space
also serves as an insulator for heat, preventing the escape of heat
from the interior of the building in winter and the penetration of it
into the structure in the summer.
[Illustration: 10. Furring Strip]
The commonest type of furring is the 1-inch by 2-inch wooden strip,
nailed to the joints of the masonry or to wall plugs inserted in
the joints. Metal furring strips are also extensively used, and
occasionally hollow terra-cotta furring blocks.
_Brick House_
Like the stone house, the brick dwelling is one of the oldest types
in this country. Examples of early brick houses show a taste for good
brick, which later died out on account of the introduction of the first
American machine-made bricks. These early machine-made bricks were
extremely ugly, due to their perfection of geometric shape, smoothness
of surface, and monotony of red color. Later improvements in the
manufacture of brick have released this material for extensive artistic
use. The surface was given a varied color and texture, and the form
was not made so machine-like. To-day we have a variety of bricks which
range in colors through reds, yellows, buffs, greens, blues, and even
dark violets. Textures of wire-cut bricks are rich and varied, and, if
properly handled, can produce the very finest architecture.
[Illustration: 11. Running Bond and method of Bonding