The Romans used a wide variety of materials ranging from chalk and sand through to pozzolanic concrete. Debris and broken pottery would be mixed with mortar in order to fill wall sections. Pumice stone mixed with concrete in order to render it lighter and so on.
Their acquaintance and expertise with such a variety of materials was partly facilitated by the extent of the empire. Their knowledgeable use is what allowed them to achieve a considerable leap in construction and Roman architecture. Having said this, it can also be said that for economic reasons the ancient Romans tended to resort to locally available materials wherever possible. Import and transport of construction materials was limited to the strictly necessary or items of high value luxury such as marble, if required.
The relative cost, available Roman technology and availability of materials had direct consequences on many aspects of Roman society. Though we won’t elaborate the point we provide an example: the relatively high cost of forged steel meant that staircases would be made of stone and/or wood which in the case of public buildings such as Roman amphitheatres would limit the geometry that could be achieved – you simply wouldn’t be able to build a tight switchback staircase, with a variety of implications: in terms of the architectural limitations and in terms of crowd control; it’s better to reduce or remove corners to facilitate crowd movements in public spaces.
The principal construction materials were: | Stone | Wood | Ceramics and Terracotta | Metal in Ancient Rome |
The use of Stone in Ancient Rome
Stone was clearly an important material for construction and the Romans were skilled in quarrying it and in using the different types of stone in different types of application. Marble would clearly be used to decorate surfaces, lime and sandstone would be used for pedestrian areas subjected to light wear whilst basaltic lava or granites would be employed for uses subjected to great stress.
The difference in these materials is not only in their relative brittleness and strength but also in other factors such as how porous and heavy they are. An interesting example of the use of stone is Alabaster which can be cut in thin translucent sheets which are capable of allowing light through whilst displaying a marble-like pattern. Alabaster applied as window panes can be still seen in a couple of the more ancient basilicas of Rome. It is worth remembering that a particular stone would be chosen not only in function of its functional properties but also in function of its appearance and overall contribution to the finished work. Where possible local materials would be used and expensive imported materials would generally be restricted for use in decoration.
As Roman dominions grew in size so too did their access to new local materials and in many cases these were used and depleted as happened with a variety of extremely precious marble varieties which are now “extinct” and only to be found as part of wall cladding or mosaics. |Back to the top |
As with stone the Romans were extremely advanced in their knowledge and use of different types of wood. The architect Vitruvius who wrote about many construction techniques, goes into some detail about when and how to cut down trees and how old these should be, how long they should be left to dry and so on. All subdivided by type of tree.
This isn’t the time and place to go into the uses and benefits of wood versus concrete and stone. In any case the Romans understood these differences and benefits well and often used wood where it was most suited. Floors, ceilings, trusses and scaffolding for construction.
Another use of wood was in machinery of war and for construction purposes. It was in these cases that the deep knowledge of the material enabled this machinery to undertake the extreme conditions and loads to which it was subjected.
Joinery: the Romans developed a full range of methods for interlocking wooden beams according to the type of wood, function of the join and application of the structure as a whole. These joins could be supplemented by a range of metal reinforcements.
Terracotta and Ceramics
The use of terracotta and ceramics allowed an immense degree of freedom in a wide range of areas of construction such as the tiling of roofs, waterproofing of pools, making vessels in which to carry and store materials and most importantly for making bricks and pipes. Ceramics were even used to substitute wood in the construction of trusses to build arches.
Although bricks tend to be softer and less durable than hard stone they are more easily carried and managed. This meant that they allowed Roman constructors a great deal of flexibility of form as well as agility and speed in construction – it is far easier for a man to shift a pile of bricks than it is to hew and carry one large stone block.
The use of bricks has tended to be a later trend in civilisation than one might think primarily because of the evolved economy required in order to render the construction of suitable large furnaces viable.
It became very common for Roman builders to use bricks, whether for flooring or wall construction. When used in floors the individual bricks would often be placed on their side in a fish-bone pattern in order to render the surface more durable. When used for walls it wouldn’t be uncommon for them to be mixed with other wall construction techniques such as stone blocks creating a sort of mixed approach. Bricks were so versatile that they allowed walls of great height and strength to be achieved relatively quickly. A very interesting example of this can be observed in the outer walls of the Pantheon where brick arches are built into the horizontal brick-work. The purpose of this was to allow a better distribution of weight coming down from above.
One final point of interest is the roman habit of stamping bricks and pipes with a seal which nowadays allows us to date the structures built very clearly. Again the Pantheon is a wonderful example of this as the bricks used for its construction allow us to date the periods of its construction and reconstruction with a degree of precision (it was burned down by fire and rebuilt by Hadrian).
The extent of Roman dominions meant that they had access to a wide variety of metals which were used throughout the empire according to their particular characteristics. The old Etruscan territories to the north of Rome were themselves rich in different metals such as iron and tin and had strongly contributed to Etruscan wealth and commerce with Greece.
Since the earliest days of Rome Etruscan metal was used across the Mediterranean to produce jewellery, particular objects such as mirrors or horse bits, small artefacts such as statuettes and of course weapons. The Etruscans themselves had become extremely skilled artisans so much so that their jewellery still holds secrets of manufacture for us. The bronze statue of the Capitoline she-wolf is itself of Etruscan manufacture.
Metal was generally an expensive material mainly because it had to be quarried out of a mine, purified, transported and worked into a useful shape by a smith. This explains why there are so few large bronze artefacts of that age in existence today: few were made and most of these were later plundered and molten. An often quoted example is Pope Barberini’s plundering of the bronze struts in the Pantheon in order to make cannons for Castle St. Angel and Bernini’s awning over the tomb of St. Peters. A few surprising examples still exist though such as the equestrian statue of Emperor Marcus Aurelius which survived the ages because it was thought to be St. Paul.
In a construction context metal could hardly compete with cheaper materials which required less handling and could usually be “produced” locally such as stone or wood. However in certain contexts its use was inevitable. Clearly it was of great use in joinery and trusses. Hard metal was also used in a number of cases in order to join stone blocks with one another and indeed to make the clasps to lift stone blocks with cranes.
In hydraulics lead metal was used both as a seal and as a material for making the pipes themselves. So much so that it has been suggested that one of the many causes of the downfall of the empire was a progressive lead poisoning of the people through excessive use of lead piping! As a seal it was placed between sections of large clay pipes. Smaller urban pipes such as those found in households would also be made of lead. Taps were made of bronze. In a very few cases lead piping was used in sections of aqueducts where fast flow and high pressure had to be achieved in order to “jump” the water over an obstacle which was too far to bridge across smoothly. Metal tanks were also used, particularly in the Roman public baths. These tanks lead sides and bronze bottoms. Like gigantic pots, fires could burn under them to heat the water before distributing it into the pools. Hard iron would be used to make tools such as hammers, chisels, wedges to assist splitting stone and wood, saws and axes not to mention a wide variety of tools used to till or otherwise work the land. These were used in vast quantities and varieties in order to dig and build foundations work and shape stone and wood, carry it into place and bind it into a durable unit.