Londinium, Architecture and the Crafts

by W. R. Lethaby

One of the advantages of coarsely-crushed tiles is that it absorbs and holds water so that the mortar made with it dries very slowly and thus hardens perfectly. In Archæologia (lx.) an analysis is given of “mortar made with crushed tiles as grit in place of, or in conjunction with, sand.” In Rochester Museum a dishful of the crushed tile is shown which was taken from a heap found ready for use at the Roman villa at Darenth. I may say here that I have found mortar prepared in this way wonderfully tenacious, and suitable for special purposes like stopping holes in ancient walls. A strong cement made of finely powdered tiles, lime and oil was used by Byzantine and mediæval builders and probably by the Romans also. Villars de Honnecourt (thirteenth century) gives a recipe: “Take lime and pounded pagan tile in equal quantities until its colour predominates; moisten this with oil and with it you can make a tank hold water.” The use of crushed pottery in cement goes back to Minoan days in Crete.

In London a long, thick wall of concrete formed between timbering was recently found between Knightrider and Friday Streets; it showed prints of half-round upright posts and horizontal planking; it bent in its course and may have been the boundary of a stream. On the site of the old Post Office a Roman rubbish pit was found, about 50 ft. by 35 ft. in size. “In late Roman times the whole pit had been covered with concrete about a foot thick and a building had been erected on the spot” (Archæol. lxvi.). At Newgate the Roman structure was erected on a “raft” of rubble in clay finished with a layer of concrete. Rubble in clay formed the foundation of the City Wall.

Fig. 3.

Many walls, described as of chalk, rubble or rag-masonry, have been found in London—one instance at the Bank has been quoted above. Chalk and flints were the most accessible material after local gravel, clay and wood. Mr. F. W. Troup tells me that “in the foundations for the Blackfriars House, New Bridge Street, we exposed a remarkable foundation (possibly not Roman). It consisted of rammed chalk, fine white material about 4 ft. wide and high, laid on great planks of elm 6 in. thick, which appeared to be sawn. These were laid side by side in the direction of the length of the wall, which ran along the west bank of the Fleet River.” I mention this, although it was probably a mediæval wall, as an example of a record; we ought to have every excavation registered. The walls of a room found in Leadenhall Street in 1830 were of rubble forming a hard concretion, with a single row of bond tiles through the thickness of the wall at about every 2 ft. in height. A sketch of this wall at the Society of Antiquaries shows it plastered outside and in. This was one of the common types of walling. Better stone walls were formed with face casings of roughly-squared little stones—what the French call petit appareil—as described above. An immense amount of piling was used in wet ground under streets and wharves, as well as walls. Foundations have been discovered of three rows of piles close together with a wall coming directly on their heads (Fig. [3]). A wall found on the site of the Mansion House seems to have had only one row of piles; it was plastered outside.

Tile Walling.—The brick commonly used in Rome was a crude or unbaked block; the burnt walling tile was, as said above, developed from pottery, and it always remained pottery-like in texture and thin in substance. As Mr. T. May has said of bricks: “They were made of heavy clay, well tempered and long exposed; the modern practice is to use the lightest possible clay right off without tempering.” Walling tiles were used in Londinium not only as bonding courses, but for the entire substance of walls. It is usual to write “Roman tiles or bricks” interchangeably, but in origin and character the thing was a tile, and, indeed, roofing tiles with flanged edges were used as a walling material occasionally. Tiles were of various sizes and shapes, but an oblong, 1½ ft. by 1 ft. and about 1½ in. thick, was most usual. In the Guildhall Museum are several triangular tiles which must, I think, have been used for facing walls with concrete cores. Solid tile walling was used in Londinium so extensively that it was evidently a common material for better buildings. The Lombard Street excavations of 1785 exposed “a wall which consisted of the smaller-sized Roman bricks, in which were two perpendicular flues, one semicircular and the other rectangular; the height of the wall was 10 ft. and the depth to the top from the surface was also 10 ft.” Here we have evidence of a brick wall rising the full height of one story at least (Archæol. viii.). Roach Smith noticed a wall in Scott’s Yard “8 ft. thick, entirely composed of oblong tiles in mortar.” Mr. Lambert has recently described some walls of brick 3¼ ft. thick found at Miles Lane. A building in Lower Thames Street had walls of red and yellow tiles in alternate layers. This fact I learn from a sketch by Fairholt at the Victoria and Albert Museum, and such use of bricks of two colours was a common practice. In Hodge’s sketches of the tile walls of a great building discovered at Leadenhall Market it is noted that some of the courses were red and buff. Price recorded of walls, 2½ ft. thick, found in the Bucklersbury excavations, that “the tiles were the usual kind of red and yellow brick.”

More recently a bath chamber has been found in Cannon Street built of tiles which on the illustration are indicated in alternate courses of red and yellow. In the description in Archæologia, it is remarked: “It would appear that the yellow was preferred, the red being employed where they were not visible.” Years ago Charles Knight observed that the tiles used in the City Wall at America Square varied from “bright red to palish yellow.” This has been confirmed by more recent accounts in Archæologia. Finally, Roach Smith, describing the discovery of a part of the South or River Wall of the City (Archæological Journal, vol. i.), says that the tiles used as bonding bands were straight and curved-edged (that is, flanged roof tiles), red and yellow in colour. At the Guildhall there are a roof tile and a flue tile of yellow colour. Building with tiles may for long have been customary, but the use of red and yellow tiles in the way described would probably have been a fashion during a limited time only, and in that case it follows that the buildings erected with red and yellow tiles are likely to be nearly contemporary; the date would, I suppose, be the fourth century. Specially made tiles were used for columns. At the Guildhall are several round tiles 8 in. diameter, suitable for the piers of a hypocaust. Also some semicircular tiles 12 in. in diameter. In Rochester Museum are some quadrants making up a circle about 1½ ft. in diameter. Tiles, eight of which made up a circle, have lately been found at Colchester, and in the Guildhall Museum is a course of a round column made up of twelve tiles around a small central circle. A large number of columns were evidently of such bricks plastered.

Fig. 4.

Arches and Vaults.—The arches in the City Wall, where it passed across the Walbrook, described by Roach Smith, were of no great span (3¼ ft.). They were constructed of ordinary tiles and were of a roughly-pointed shape. Arches of this form were not infrequently used in Roman works; they were not the result of inaccurate building. About a dozen years ago a well-built pointed arch of alternate tile and tufa, found at Naples, was described in Archæologia. The tiles, although thin, were sometimes made slightly wedge-shaped, and the city gates at Silchester seem to have had arches of such bricks.