The third class of dwelling is quite rare, and very few small houses
are built that could be classified under it. Some builders call them
fireproof houses, although this is erroneous. These buildings have
walls, roofs, floors, and partitions built of incombustible materials,
but the finished floors, the trim, windows, and doors are of wood. The
exterior walls are of masonry construction, and the construction of
the floors and roofs consists of steel beams with terra-cotta arches
or concrete floor slabs, spanning in between them, and the partitions
are of terra-cotta, gypsum, metal lath and plaster, or other similar
materials. They may also be built of reinforced concrete throughout,
or any other combination of these materials. There have been very few
examples of this kind of construction used in the small house. It is an
unfortunate condition that it is more adaptable to the costly mansion
than to the average house of the middle-class citizen, for the high
cost of construction of this character, in most cases, permits it to
be used only by the wealthy man. Examples where such houses have been
built generally show an investment of $30,000 or more, or, if they
were built to-day, $50,000 or more. Those attempts to use this form
of construction in the small house have been made by large building
corporations, and have been chiefly represented by concrete houses of
very ugly design.
[Illustration: Type III. Walls, floors, partitions fireproof, but
windows, doors and trim of wood.]