What were ancient Roman houses made of?

After we have already devoted ourselves to building materials in antiquity and to Roman architects, we will take a look inside the house in the third part of our mini-series.

The floor

Once the building had reached its finished shape, i.e. the walls and roof were finished, the interior work began. First of all, the floors were laid with screed. For this purpose, the existing ground on the ground floor was leveled and compacted by tamping. A mortar made of gravel and lime in a ratio of 3: 1 was poured onto this smooth surface, which was then tamped. This layer was about 23 cm thick (three quarters of a foot in Roman units), on top of which was the main layer (nucleus), consisting of three quarters of brick rubble and a quarter of lime. This was usually about 11 cm thick (6 fingers in Roman units).

The uppermost, the visible layer of the floor was then placed on top. It usually consisted of stone slabs, mosaics, or stones laid in a herringbone pattern (opus spicatum). At thermal baths or the houses of wealthy citizens there was underfloor heating under the floor (more on this next week in our last part of the series). In order to obtain a permanent mosaic, the stones were placed in the damp mortar. The responsible worker (the "mosaicist") divided the area to be worked into day works. For the mosaic itself, a template was drawn or scratched on the screed. This design was then filled with the mosaic. The mosaic stones (tesserae) were made of natural rock, ceramic, or glass and were usually about 1 cm² in size, although there were deviations from this size.

Image: Mosaic in Carnuntum

doors and windows

Although every house in Carnuntum probably had a door, only a very few doors and windows have survived. The simple explanation: Wood rots over time, so that the doors of Roman houses are often recognized by the doorsteps and not by the doors themselves, as these are often no longer there after almost 2,000 years. However, doors are usually very easy to document, as iron fittings, locks and keys are known and they can withstand longer periods of time without rotting. Other good clues are the stone sleepers, which are also more durable than wood.

It is more difficult to determine the shape, size and position of the windows, because the walls of the ruins usually do not reach high enough to reveal the dimensions. Only comparisons with Roman representations on mosaics or wall paintings, which are also used for the appearance of the doors, help here. In addition to practical considerations, the presence of the windows is proven by numerous finds of window glass in the archaeological findings.

Roman window glass

Based on finds from Pompeii and Herculaneum, it is assumed that window glass (specularia) first around the middle of the 1st century BC Christ was made in Italy. The emergence and further spreading are likely to have been related to the emergence of the large thermal baths at the beginning of the imperial era. There the large glass windows, divided by bars, soon became part of the standard equipment. In private residential construction, window panes became a clearly visible status symbol from the 2nd century AD, as they were not affordable for everyone.

Flat glass, which was used in the windows of the time, could be made in two ways. Cast glass, which has also been proven in Carnuntum, dominates among the finds. The hot glass mass was poured into a mold made of stone, wood or mortar. The cast glass is rough and matt on one side, while the side facing away from the casting mold often shows tool marks, which probably originate from pulling the viscous mass to the edges and corners of the mold. These discs are usually relatively thick (up to 6 mm) and have sides of 23 to 33 cm. Due to the impurities in the production process and their comparatively great thickness, these disks had a milky appearance and were not transparent.

In the second manufacturing technique, the cylinder blow molding process, a bottle-shaped, blown blank was cut lengthwise and smoothed. This makes the panes significantly thinner (up to 3 mm) than the cast glass, which leads to a significantly better light transmission. This process remained in use until modern times.

Image: The Villa Urbana in Carnuntum

Roman wall painting

Wall painting was common throughout the Roman Empire and was found in both private and public buildings. The paint was applied over several layers of plaster and made from different materials. For example, purple was obtained from animal substances, the color red from plant substances such as the root of Rubia Tinctorum. Inorganic substances were also used (for example: cinnabar).

As with the mosaic, scratches were made in the damp plaster or strings were stretched, which served as orientation and divided the areas. The colors were applied to the still damp plaster mortar using the fresco technique or to the largely dry plaster surface using the Secco technique.

In Carnuntum is also still through finds in theVilla UrbanaPainting demonstrated in the elaborate technique of Stucco Iustro, in which the paint layer was applied to a damp plaster made of lime water and marble powder that was already colored with pigments. By smoothing and compacting the surface under the action of pressure, a gloss was created that could be enhanced by a beeswax emulsion. This technique became very famous because it is best known from Pompeian wall paintings.

Part 1: Building materials in ancient times

Part 2: Architects in antiquity


CM. Behling: Wall painting research in Carnuntum (Lower Austria). Overview of the results so far, ActaArchHung 60, 2 (2009).

CM. Behling: Wall painting finds from the excavations in the area of ​​the villa urbana in the Carnuntiner civil town, AÖ 20, 1 (2009).

J. Komp: Roman window glass. Archaeological and archaeometric investigations into glass production in the Rhine area (2009).

Henner von Hesburg: Römische Baukunst (2005).

Heinz O. Lamprecht: Opus Caementitium. Civil engineering of the Romans (1996).

Jean-Pierre Adam: Roman Building. Materials and Techniques (1994).

Vitruvius: Ten Books on Architecture, Reclam. ed, Fensterbusch (1996).