Building Materials And Construction Methods
The Romans primarily used a variety of stone and earth materials in their construction.
The main building stone for the early Roman years was tufa, a soft and brittle
stone that was found extensively around Rome. It could be quarried with bronze tools, and
came in a variety of colors which were often used decoratively. Being soft, the tufa
often weathered poorly and had to be protected with a stucco covering. As construction
technology progressed, other types of stone were used as they were discovered. Peperino
stone was a mixture of volcanic ash, gravel and sand, harder than tufa and more
fireproof. Travertine was stone consisting almost entirely of lime, even harder
than peperino, but susceptible to fire. Silex was a very hard rock made of
lava, but it was so hard that it was difficult to produce, so it was not used much in
buildings.
The Romans cut these stones into rectangular blocks, two Roman feet square by four feet
long. Walls were built from these stones, laid in alternating courses of headers and
stretchers until the wall was complete. In most early Roman construction, mortar was
rarely used, the blocks being so smooth it was not necessary.
This shows a small temple constructed with blocks of peperino. The seams in the
walls are visible due to the lack of a covering, but the blocks are very smooth and the
structure is still in excellent condition. After the decline of the Roman empire, many of
the Roman works were taken apart and the excellent raw material they contained was reused
in local structures.
During the first century BC, a volcanic ash called pozzolana was discovered. This
discovery allowed concrete to be made for the first time, consisting of the ash, lime, and
broken fragments of stone. Pumice could be added to make a lightweight mixture. The
discovery of concrete allowed the Romans to build vaults and domes, structures that needed
a strong yet lightweight material that could be molded as desired. Pieces of broken
pottery were also used in the concrete mix, since they were plentiful in Roman cities.
Concrete walls were build similarly to the modern way. A lumber framework was put in
place, then the concrete poured in a semi-fluid state. Once the concrete set up, the
frames were removed. Another technique of wall building was two parallel thin stone walls,
the space between being filled with rubble and concrete. This kind of composite structure
gave great strength with less expensive stone usage.
This shows a wall, composed of small pieces of rubble concreted together, with a facing of
more regular larger stones.
Kiln-baked bricks were used early in the empire for construction, but soon faded to use as
facings or decorations. They were of amazing quality, hard enough to able to strike fire
like piece of flint. Also the bricks found at the far reaches of the empire are of equal
quality to those from Rome, showing the consistency of Roman imperial quality control.
The walls were usually faced with smaller stones or bricks set in concrete, covered by
stucco or plaster. The stucco was a more utilitarian finish, while the plaster could be
polished and colored with pigments. This slide shows small tufa blocks set in the
walls as facings.
Marble, which was used widely by the Greeks, was rarely used for construction, being
reserved for floors, walls coverings, and decorative figures.
The Romans used scaffolding extensively in their construction. The square holes used for
the beams supporting the scaffolding can be found in most concrete fixtures and quarried
into some of the stone blocks.
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