Roman wall construction

Although there is some evidence that lime was used as a plaster by the Egyptians, it was the Romans who moved from creating dry stone walls (or Cyclopean) walls, onto to sun dried brick walls. These solid walls were built with a base or socle of massive stone upon which sun-dried mud bricks were placed and bonded together with mud, to create solid one or two layer brick walls.

It was through the development of a mortared rubble construction called opus caementicium that the Romans moved towards solid walls with roman concrete construction, which was quicker to build with. By around 150 BCE the Romans commonly used lime as mortars to build solid stone walls. These walls were also solid but made up of two layers built concurrently for speed, firstly an inner core of small stones in mortar (caementa) and then a facing layer of stoneor brick.

Different names were given to the different facing finishes through the different period; Opus incertum a small blockrandom pattern, Opus reticulatum a rectilinear horizontal pattern of stones, Opus testaceum a brick faced concrete and Opus mixtum rectilinear strips of stones and bricks.

A significant number of Roman remains from forts to amphitheatres and to gateways and temples can still be found around the UK, any of which highlight their use of solid stone construction, whilst some near complete buildings can also be found. The lighthouse at Dover Castle, of the old Roman port of Dubris is one of only 3 remaining and still standing Roman lighthouses in the world, and made of solid stone with mortar, as well as largest surviving gateway of Roman Britain at Colchester.

It is worth noting that although many Roman walls may have been constructed as solid layered finished walls, in his monumental set of books, De architectura (On Architecture) Marcus Vitruvius Pollio, wrote possibly the first handbook for Roman architects and indeed possibly the first mention of the benefits of adding a cavity.

“…if a wall is in a state of dampness all over, construct a second thin wall a little way from it…at a distance suited to the circumstances…with vents to the open air…when the wall is brought up to the top, leave air holes there. For if the moisturehas no means of getting out by vents at the bottom and at the top, it will not fail to spread all over the new wall.”

Marcus Vitruvius Pollio, De Architectura; The Ten Books on Architecture, Book VII, Chapter IV, On Stucco Work in DampPlaces; Translated by Morris Hicky Morgan, Harvard University, Harvard University Press, 1914. Vitruvius wrote in the time of Augustus (63 BC – 14 AD) and it is believed that he wrote this around 15 BC.

“this we may learn from several monuments…in the course of time, the mortar has lost its strength…and so the monuments are tumbling down and going to pieces, with their joints loosened by the settling of the material that bound them together… He who wishes to avoid such a disaster should leave a cavity behind the facings, and on the inside build walls two feet thick, made of red dimension stone or burnt brick or lava in courses, and then bind them to the fronts by means of iron clamps and lead.”

Marcus Vitruvius Pollio, De Architectura; The Ten Books on Architecture, Book II, Chapter VII, Methods of Building Walls, 15 BC.

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