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Motorway Archaeology --
Medieval Tile Kiln at Addington, Kent.
In 1970 work began on the M20 extension from Aylesford to Wrotham Heath a total distance of about eight miles. Watch on the topsoil stripping and subsoil excavations was left in the hands of local people who gave constant assurance that all was being carefully patrolled. On 9th May, 1970 at the suggestion of one of the motorway engineers (when the soil stripping programme was substantially complete) a special team from the West Kent Archaeological Group made a snap inspection of one mile of the route at the west end of the new Motorway.
Within an hour indications of three possible sites were located. The first was a light scatter of flint implements and waste material on the north side of the Motorway line. The second consisted of two Romano-British potsherds of 2nd century date from the south side of the Motorway. Finally, a substantially complete medieval tile-kiln was located in an isolated position right in the centre of the west-bound carriageway, which judging by the grass growing from its walls, had been exposed some weeks earlier during the topsoiling process. Quite clearly a great deal of information about these sites (and probably others too) had already been destroyed without record. Equally significant, perhaps, the line of the south fence of the Motorway passed within 350 feet of the famous Chestnuts Megalithic Tomb and only 500 feet from the Addington Long-Barrow! Without doubt this length of motorway needed responsible full-time archaeological watch which did not exist in 1970, but which was eventually created by the Kent Archaeological Rescue Unit in 1973. The kiln was excavated on 10th and 11th May, 1970 and subsequently destroyed by the road operations.
The site (NGR 5638 1588) of this kiln lay in what had been an open field in the parish of Addington, Kent about one mile west of St Margaret's Church. The kiln had been built into a gentle south-facing slope, on a clay-based soil relating to the Folkestone Beds at an elevation of about 230 feet OD.
In plan (Figure 1) the kiln was rectangular being 13 feet by 10 feet 8 inches overall including the walls which were 20-24 inches wide. It consisted of a pair of parallel rectangular chambers divided by a central spine wall, also 2 feet wide. The chambers were completely closed on three sides and partially closed on the fourth by the bases of what had been arched flues. The walls were built largely of fragments of medieval roof- tiles laid flat, but the core also contained fragments of local sandstone. Although the west wall had been destroyed by bulldozer operations, the remaining walls survived to a height of between 10-20 inches.
In detail the west chamber was 7 feet by 2 feet 5 inches internally compared with the 7 feet 4 inches by 2 feet 5 inches of the east chamber. The bases of the arched flues projected 6-7 inches from the spine wall to which they clearly butted. All four were about 12 inches wide and each pair flanked an arch 16 inches wide. The spine and side walls continued beyond these arch bases, with the spine wall, at least, ending 3 feet further on. Here the ground level started to drop away in what was probably a stoke-hole. The floor of the structure was of clay burnt to a hard, cindery texture and this was covered by a layer of fine ash one inch deep. The walls were generally coated with a purple-black glaze or vitrified substance, which probably had sweated out of the structure during the firing of the kiln. The chambers of the kiln were found to be filled with a mass of broken roof tile fragments and pieces of sandstone, both probably representing parts of the collapsed superstructure. The tile fragments again represent roof-tiles mostly with a width of about 6.1 inches. Two of the tiles from the western pier of the east chamber measured 10.2 inches, in length, 6.2 inches in width and were 0.5 inches in thickness. Each had a pair of peg-holes, spaced 2.5 inches, apart, about 0.8 inches from one end.
The Adjacent Area.
No trace of any other structure was noted in the immediate area, though the whole of the area to the north had already been removed by the scraping machines. A light scatter of roof-tile, similar to that in the kiln structure, was found for at least 80 feet to the south, 50 feet to the east, 30 feet to the west and for a minimum of 10 feet to the north. At a point about 36 feet south of the kiln centre the machines had revealed a mixed deposit of brown loam, sandstone rubble, roof-tile and carbon. Apart from being at least 2 feet deep its limits were not determined owing to the presence of dumps of soil. It may have represented the fill of a clay-pit adjacent to the kiln. Several small potsherds associated with this material seem to be from vessels of 13th or 14th century date.
There can be little reasonable doubt that this structure represents a kiln of medieval date. Its double-chambers, tile-built walls and arched flues are all features typical of medieval kilns in Kent and the absence of other material surely points to the manufacture of roof tiles. The Group excavated a kiln at Hartley in 1963 See (Reference 1) which was of similar form and probably of 13th or 14th century date. The Group also excavated a rather more elaborate tile-kiln at Keston in 1972 See (Reference 2) which probably dated from the 16th century and was an evolved form of the Addington kiln. Another kiln was excavated at Tyler Hill by the writer in 1967 See (Reference 3) and this too is similar in form and date. Other kilns at Tyler, excavated by Gerald Cramp and Duncan Harrington See (References 4 and 5), were also associated with an industry producing pottery and floor-tiles of 13th and 14th century date. It is to be regretted that the failure locally to watch the motorway operations over a period of weeks almost certainly resulted in the loss of a great deal of additional information and evidence.
The Group gratefully thanks Mrs M Altria for preparing the plan of the kiln for publication.