What are Roman thermae?

Thermae (Latin, from the Greek thermos, “warm”) were the large public bath complexes of ancient Rome, with a sequence of rooms ranging from cold to hot water, often combined with exercise yards, gardens and meeting spaces. They were far more than a place to wash: they were social centres where people exercised, did business and met friends. Smaller bath houses were called balnea.

Layout

Visitors usually followed a fixed route:

• Apodyterium: changing room.
• Frigidarium: cold baths.
• Tepidarium: lukewarm room to get used to the heat.
• Caldarium: hot room with warm-water pools.
• Laconicum or sudatorium: dry sweating room (in larger complexes).
• Palaestra: courtyard for sport and games.

Building technique

• Hypocaust: the floors of the warm rooms rested on small brick pillars (pilae). Hot air from a furnace (praefurnium) flowed beneath the floor and rose through hollow wall tiles (tubuli).
• Vaults and domes: the great halls were roofed with barrel vaults, groin vaults and domes of Roman concrete, creating large spaces without intermediate supports.
• Water supply: aqueducts and reservoirs delivered the water.
• Orientation: the warm rooms were preferably placed facing south or west, to benefit from the sun’s heat.

Well-known examples

• The Baths of Caracalla and the Baths of Diocletian in Rome, among the largest bath complexes of antiquity.
• In the Netherlands, the remains of the Roman bath house of Coriovallum (Heerlen) can be seen in the Thermenmuseum.

The principle of the thermae lives on in the modern sauna and spa.

Related terms

• Hypocaust
• Roman architecture
• Aqueduct
• Barrel vault
• Groin vault
• Dome

Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.