The Lost Port of Londinium - Page 3
By Alistair Douglas, Senior Archaeologist, Pre-Construct Archaeology Ltd.
Graphics by Josephine Brown
All photos by Pre-Construct Archaeology Ltd
The hypocaust system
Hypocaust systems were generally constructed of stacks of bessales bricks built at appropriate intervals to enable bipedales bricks to bridge the stacks, and create a base for a 0.20 - 0.40m thick suspended floor (suspensura). The stacks of tiles in the heated rooms, known as pilae, were built on compacted sand and gravel sub-floors.
No in-situ flooring survived, but collapsed opus signinum may represent the floor surface itself, or a bedding layer for another material. The surface was fairly smooth and appeared finished. Because of the waterproof qualities of this type of floor it would have been ideal for use in the baths. Opus spicatum bricks and tesserae found on top of, or close to, the bathhouse may indicate that the structure had herringbone and some mosaic flooring in addition to opus signinum.
The under-floor space would have been heated by a furnace (praefurnium) commonly housed in a structure adjoining the main building, or in an internal room near the outside wall. This peripheral location resulted from the constant necessity of supplying fuel and maintaining the fire. The hot air, heated by the fire, would flow under the floor, and was drawn up through the walls by means of specially designed hollow rectangular flue tiles (tubuli) behind the interior render and wall finish. The hot air passed from room to room at sub-floor level via flues penetrating the walls. When coupled with the maintenance of non-stop slow-burning fires, these systems, would have provided a very effective method of heating.
In the original build the hypocausts of the eastern suite of heated rooms were all linked by the insertion of flues. The western tepidarium is likely to have been connected to heated rooms to the west in a similar fashion but these lay beyond the limit of excavation. The flues commonly comprised a simple opening in the sub-floor wall, near to the base of the hypocaust. Most had vertical abutments, framing openings ranging in width from 0.32m to 0.40m and were usually faced with tile and brick, intended to channel loads from above and to withstand high temperatures. Only one flue linking the apse to the main building, remained completely intact. It was built on a lacing course of brick and tile running through the north wall. The abutments were constructed entirely of fragmented brick and the roof of the flue was pitched, consisting of two whole bricks placed on-end, forming a triangular apex.
Other much smaller flues were formed of tubuli running through the walls located just below the suspensura. In one instance the tiles not only penetrated the walls but also linked with others running horizontally around the inside of the room heating the walls. Further tubuli would have continued up to the roof where the heat was probably vented through chimneys.
Accommodation for the clients
Immediately adjacent and north of the bath-house lay an open yard. This external surface may have been part of a exercise yard or palaestra, a service yard, or even an entrance-way to an accommodation block. Makeup layers to the yard surface are thought to be contemporary with the primary phase of the bath-house and pottery from them suggests a deposition date after AD 240.
The yard was partly enclosed to the north and west by an accommodation block, a clay-and-timber building with reasonably well appointed rooms, although the opus signinum mortar floors were in a degraded state at the time of excavation. The floors showed signs of repeated repair and partial resurfacing with beaten earth indicating a degree of care and maintenance. The recovery of red painted wall plaster was an indication that the walls were rendered and decorated. Some of the rooms were provided with a hearth, presumably for heating or cooking. Throughout the use of the bath-house these clay-and-timber buildings were regularly maintained and rebuilt. This occurred wholly, or in part, at about 10 year intervals. It was in these buildings that much of the pottery, and most of the other artefacts recovered from the site, were found. The finds assemblage was particularly rich, and included a stone palette for
mixing cosmetics, 82 hair pins, jewellery including copper alloy finger rings, jet bracelets, a gold earring and part of a necklace.
Read about the Phases of the bath-house on page 4.
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