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Hypocaust at Bath

Hypocaust at Bath

CC Flickr User Alun Salt.

The word hypocaust refers to a subfloor radiant heating system: suspended floor with space for gases and hot smoke. The word hypocaust comes from the Latin hypocaustum which originally meant a 'burning underneath'.

Hypocausts were vital to the ancient Roman system of central heating that made the baths hot and heated other large rooms. In addition to the hypocaust, there were sometimes hollow walls to help maintain even temperatures and prevent condensation.

The small pillars of stacked bricks, shown in the accompanying photo of a hypocaust at Bath, the ancient Roman Britain site, would have supported a fireproof floor that was heated by means of air circulation in the underfloor chamber with an external furnace as heat source. Ring (see references) suggests the hot gases at the top of the hypocaust below the floor would have been up to about 400° F, with the floor and wall surfaces about 100° F.


  • "Sergius Orata: Inventor of the Hypocaust?" Garrett G. Fagan. Phoenix, Vol. 50, No. 1 (Spring, 1996), pp. 56-66
  • "hypocaust system" The Concise Oxford Dictionary of Archaeology. Timothy Darvill. Oxford University Press, 2008.
  • The Celt, The Roman, and The Saxon
  • "Windows, Baths, and Solar Energy in the Roman Empire," by James W. Ring. American Journal of Archaeology, Vol. 100, No. 4 (Oct., 1996), pp. 717-724
  • "The Open Rooms of the Terme del Foro at Ostia," by Edwin Daisley Thatcher. Memoirs of the American Academy in Rome, Vol. 24, (1956), pp. 167+169-264
Also Known As: suspensura
Alternate Spellings: hypocauston
Cicero's contemporary Sergius Orato is often credited with inventing the hypocaust, but there were similar structures well before his time.

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