A typical Roman bath was more than a pool of water; it was a community facility consisting of toilets, an exercise courtyard, changing rooms, hot and cool bathing chambers and often a stadium. These amenities required a constant supply of water, heat and a strong infrastructure. Roman baths were engineered using innovations such as aqueducts, hypocaust heat, vaulted ceilings and concrete.
The Romans used aqueduct technology, borrowed from the Greeks, to bring water to the baths. Using gravity to pull the water downhill, many aqueducts ran through covered trenches and tunnels to remain hidden from enemies. Pressurized pipes acting as inverted siphons were used to pull water upward in deep valleys. Arcades, which were large bridges built with a series of arches, kept the flow of water raised high above populated places.
To keep baths hot, Roman engineers developed the hypocaust heating system. A marble floor was raised on pillars, then heated with a log fire.
Baths grew larger with the Roman development of vaulted ceilings. Vaulted ceilings were made in a solid mass with concrete. This new design enabled Roman architects to build roof structures that could support vast spaces. Smaller public baths could house a few hundred bathers, while these larger structures could accommodate thousands at a time.
The innovation of concrete was used extensively in the construction of Roman baths. The Roman architect Vitruvis created concrete by mixing lime with water to form a powder. By adding more water to the powder mix, a paste is made that binds to rocks and sand which can then be molded and hardened. In making bath structures, volcanic ash or crushed tile were often added to the concrete to provide waterproofing.
