The Roads of Ancient Rome: How Were They Built?

How Roman roads were made

• Foundation soil – depending on the terrain, builders either dug depressions on level ground or installed special supports in places where the soil subsided. The soil is then compacted and sometimes covered with sand or mortar to provide a stable footing for the multiple layers above.
• Statumen – a layer that was laid on compacted foundation soil, consisting of large rough stone blocks. Cracks between the slabs would allow drainage to be carried through. The thickness of this layer ranged from 25 to 60 cm.
• Rudus – a 20-cm-thick layer consisting of crushed rock about 5 cm in diameter in cement mortar.
• Nucleus – a concrete base layer made of cement, sand and gravel, that was about 30 cm thick.
• Summum dorsum – the final layer consisting of large 15-cm-thick rock blocks. But more often fine sand, gravel, or earth was used in the top layer, depending on the available resources at the workers’ disposal. This layer had to be soft and durable at the same time. Paved roads were very expensive and were typically reserved for sections located near and inside important cities. When pavement (pavimentum) was used, large cobblestones of basalt laval were typically used in the vicinity of Rome.