ULAS
University of Leicester Archaeological Services

Roman building materials

Whilst the public buildings of Roman Leicester such as the Jewry Wall bath house and the macellum (market hall) were constructed of stone, many townhouses were probably made using dried clay bricks rendered with plaster, and the poorer housing and shops would often have been made of timber and roofed with thatch.

Because timber is rarely preserved we know more about the way that the public buildings and richer townhouses were built because they also incorporated ceramic tiles or stone slates, wall plaster and tessellated or mosaic stone floors.

Ceramic tiles were used in three ways, predominantly for roofing and as levelling courses in masonry walls, but also within the heating systems of the richer town houses and bath buildings where they provided heating ducts and floor supports.

As shown above, a roof was tiled by arranging flat tiles with side flanges (tegulae) in overlapping rows along the battens (some nailed down) and then placing curved tiles (imbrices) vertically over the abutting flanges to make the roof watertight. Curved ridge tiles, similar to the imbrex but not tapering, sealed the rooftop.

Diamond-shaped ‘Swithland’ slates, quarried from near Groby, were also used for roofing (shown left). Care was taken in dressing the slate and ensuring that the visible corner was a rightangle. Incised lines were sometimes used as a guide to where the suspension hole should be placed.

Walls were rendered with plaster, with the top layer smoothed and painted with a variety of geometric patterns, architectural features, figures, or greenery.

Concrete flooring (opus signinum) was often decorated with tessellated or mosaic pavements. Tesserae are the individual cubes of sandstone or broken tile, laid in mortar to form grey and red geometric patterns in corridors, whilst in dining rooms and bath suites, finer blocks of different colours were used for the central mosaic design. Tiles could also be laid on their sides to form a herringbone pattern (opus spicatum).

Underfloor heating systems (hypocausts) used tile in two ways. Flat square bricks were used in stacks (pilae) to support the raised concrete floor and thus allow the hot air from the external furnace to circulate with the floor acting as a storage heater (see photo, right). Boxflue tiles (tubulus) then drew the hot air up inside the walls and out through chimneys in the roof.

Large rectangular flat bricks (lydion), similar in size to the tegulae, were incorporated into masonry walls as levelling courses or decorative arches, which helped to stabilise the structure of facing stones and a rubble and mortar core. Examples of these are shown right.

Roman ceramic tiles were made using sanded formers of wood. Individual tile makers used finger signatures to identify their work or, in the case of flue tiles, distinctive combed or rollered patterns impressed while the clay was still wet. Before firing in the kiln, tiles were laid out to dry and this is when the accidental impressions of human and animal footprints were left, the subsequent firing ensuring they survived for us to see. Young children, dogs, cats and sheep roamed free across the tiler’s yard.

Left, finger signature and paw print, and above, hobnail print on tile