An overview of building materials in ancient Rome and ancient Roman construction – with supporting images and a sense of progress through time, different types of building materials, their qualities and uses.
Building materials in ancient Rome were varied and used with great knowledge of how to achieve the best result from their qualities. The use of materials evolved in accordance with access to the materials as well as wealth and skills to process them. From the earliest pastoral kingdom through to the Roman republic there was a shift towards the use of brick and aggregate materials. Internal decoration might go as far as mimicking certain types of stone cladding but the use of marble was rare in comparison to later centuries. Access to extended dominions and wealth during the Empire enabled a flourishing market in more expensive and exotic varieties of stones and marbles.
Huge revamp of the City of Rome: A step change which can be considered an architectural revolution was during the reign of Emperor Augustus with the discovery of new forms of cement. This coincided with the emperor’s enormous investments in civil engineering and architecture to renew the infrastructure of Rome. These attracted architects and workmen from across the empire to work on multiple projects. The writer Suetonius recorded Augustus’ words: “I found Rome a city of bricks and left it a city of marble”.
Great Fire of Rome: The advancement of building material technologies was also driven by other great events, such as for example the great fire of Rome in 64AD. This drove Nero’s magistrates to create new construction codes defining health and safety measures, such as the distances between structures (as fire breaks) or the means by which concrete might be faced with brick in order to induce greater fire resistance.
Quarried materials such as chalk, sand and pozzolanic ash were leveraged with the greatest ingenuity in concrete or even dry-stone construction. Debris and broken pottery would be mixed with mortar in order to fill wall sections. Pumice stone or porous Tufa rock mixed with concrete in order to render cement lighter and so on.
Their acquaintance and expertise with such a variety of building materials were partly facilitated by the extent of the Roman empire. Their knowledgeable use is what allowed them to achieve a considerable leap in construction and Roman architecture. For economic reasons the ancient Romans tended to resort to locally available construction materials (and cheap labour!) wherever possible. Import and transport of construction materials was limited to the strictly necessary or to high value luxury items such as marble.
The relative cost, available Roman technology and availability of building materials in ancient Rome 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 iron 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 use of Stone as a building material in Ancient Rome
Stone was clearly an important material for construction and the Romans were highly 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.
Rome had a considerable quantity of rocks associated with Volcanic activity. An extremely common building stone in Rome is a form of compressed volcanic ash – igneous rock – called “Tufa” rock, also known as Tuff, which is relatively porous, light and of medium hardness. It is relatively unsightly but extremely suitable for sturdy structures, such as foundations. It could even be easily cut to form types of bricks which could be used for a particular type of wall construction called “opus reticolatum”. The image shows an example of this, and also gives a sense of how a wall might have a core filled of a general mortar and rubble mix. The rubble could also include broken pottery sherds – recycling at its best!
As Roman dominions grew in size so too did their access to new local materials. 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.
Marble in ancient Rome
Marble deserves a special mention among the stone building materials of ancient Rome: For many centuries a relatively beautiful white metamorphic local rock was Travertine marble – not quite as prestigious as ‘proper’ marble in that it is full of veins and cavities, but it is durable. Harder than tufa though not as strong as Basalt. Travertine had both structural as well as aesthetic qualities. So for example the Colosseum’s structure had tufa/brick bearing structures and Travertine visible features.
Higher quality and expensive marbles became available as Roman dominions grew. Emperor Augustus is famed for having said that he took “a city made of brick and left one of marble”. With the progression of the Empire there was increased wealth and access to many type of foreign marbles, some of which have since become depleted. The ability to work the marble was also extremely sophisticated so that it could be employed in highly elaborate mosaics and “crustae” decorations. The image below gives a sense of this when we consider that this piece of marble is cut to only a few millimetres thin and perfectly plane, so that it would be perfectly suited for beautiful cladding of a wall surface.
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 the machinery of war and for construction purposes. It was in these cases that the deep knowledge of the material properties 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.
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.
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.
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. The Pantheon is a wonderful example of this, as the bricks used for its construction allowed us to date the periods of its construction and later reconstruction with a degree of precision – it was burned down by fire and rebuilt by Emperor Domitian and later to its present form by Hadrian).
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. In particular circumstances ceramics were even used to substitute wood in the construction of trusses to build arches.
As with Cement, during the first century AD there was a revolution in the production of glass. Glass was often more closely associated with vessels and personal wares but it could also be employed in the building industry, for example to make windows or mosaics. Roman glass was developed to an extremely high degree of workmanship and expertise for a broad variety of fields.
Metal in ancient Roman buildings
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: Some was intercepted on its way to Constantinople at the end of the Empire, and the rest in later times to make cannons for Castle St. Angelo, 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 as 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.
Metals in hydraulics
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 the 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 had lead sides and bronze bottoms. Like gigantic pots, fires could burn under them to heat the water before distributing it into the pools.
Metals for tools
Tools 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. Hard iron would be the preferred material 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, though sharpened flint could also be used as a substitute in various situation such as to till land.
The Romans had good working knowledge of a range of plasters and mortars with which to bind bricks or create the smooth facing required to paint a wall. However these tended to be lime mortars, susceptible to the effects of damp leaching which could weaken them.
Roman cement deserves and entire book to itself. The discovery that pozzolanic volcanic ash could turn lime mortars into a hard water-resistant cement was revolutionary for Roman engineering, not only enabling stronger construction but also different approaches to situations involving underwater environments.
A proper architectural revolution ensued in the early part of the first century AD, as new means of utilising this technology together with other aggregate materials like tufa or pumice stone in new structural forms and situations were put to the test. Arches, domes, dams and multiple other structures were realised which had never previously been possible.
Whilst Cement was the big game-changer, it was access to wealth coupled with engineering technology and embellishment that led Emperor Augustus to say
“I found Rome a city of bricks and left it a city of marble”.
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