20 Apr Brickwork, An overview
Spencer Hall ACR
Bricks have been used as a building medium for millennia, the earliest known brick buildings dating back to around 10000BC, The Encyclopaedia Britannica lists the oldest known brickworks as being Samarian, sited between the rivers Tigris and Euphrates which flow from the mountains into the Persian Gulf. The earliest bricks were not fired, but were formed from wet mud and earth then air/sun dried until solid.
Bricks were first introduced into Britain by the Romans, but they were not used for domestic buildings until around the 14th Century. The Romans adapted the production process from that which had gone before, by firing their bricks in a kiln rather than by drying them naturally. Fired bricks were found to be much more resistant to inclement weather (suiting the English climate), which made them a much more reliable material for use in permanent structures. Fired brick also benefits from greater thermal properties – absorbing heat generated throughout the day, retaining it and releasing it at night.
An overview of the history of bricks & identifying the age of historic brickwork…
Bricks as we know them, are a mixture of clay and sands which are mixed with water to create a consistency suitable to mould. Too much moisture and the brick will shrink and crack, too little and the material is unworkable. Additives can be added such as; lime, ash or organic matter, which speeds up the burning of the brick, but too much can cause distortion and in turn lead to failure. Traditional bricks were generally made from vernacular materials, as transport was both time and resource heavy – this meant using sands and clays in close proximity to settlements (or more likely building settlements close to the availability of material). The Romans discovered that very clean clays were produced from dredging rivers. These Alluvial clays are produced where sedimentary deposits are laid down and develop into a clean fine material which requires very little processing. It is thought that most Roman bricks are made from this material, as was confirmed with bricks produced for The London Temple of Mithras circa 250AD. This clay was collected from The Wallbrook tributary which ran off The Thames and was possibly a leading factor in the siting of Londinium.
As Alluvial clays are not widely available these days (although some do exist and are still collected), modern bricks are often made using clays from different sources which give differing properties to the firing. This blending process reduces the possibility of impurities from one clay source affecting the overall quality of the finished product. Similarly, the standardisation of the manufacturing processes permits the manufacturer to limit variations due to processing and to produce a more uniform product.
The properties that most concern the users of brick are on the whole (and in no particular order) durability, colour, texture, size variation, compressive strength and permeability.The mixed material is then thrown or pressed into a mould (or extruded in modern manufacturing) and allowed to dry naturally until ‘leather hard’. The Romans preferred to make their bricks in the spring and then stored them for up to for 2 years before they were used or sold.
Using mobile kilns, the Romans were successful in introducing kiln fired bricks to the whole of the Roman Empire. The kiln fired bricks were generally 1 or 2 Roman foot long, but with some larger bricks at up to 3 Roman feet. These were mainly flat, broad thin sections, not unlike a tile, which is probably why they ‘burnt’ so well, and have survived so well for many centuries. The smallest 1 ft. sections were known as Bessalis, the largest two foot square as Bipedalis and the ones between Sesquipedalis. Over time, the size of bricks developed into something closer to those we know today with the size being generally based on the approximate size of a man’s hand which made handling and laying much easier.
In general terms, early brickwork, in a period when no standardisation of bricks existed, used thick mortar beds in order to compensate for the irregularity in brick sizes – this allowed the bricklayer to regulate the small differences which arose during the build and maintain consistent levels. Some early medieval bricks were as big as 13″ x 6″ x 2″. Late 15th century bricks were mostly about 9½” x 4½” x 2″. A charter in 1571 specified 9″ x 4½” x 2¼”, and in the 18th century, Parliament decreed a size of 8½” x 4″ x 2½”, which is modern equivalent to the metric brick size of 215 x 102.5 x 64mm.
Another major boost to their use was undoubtedly The Great Fire of London in 1666. It burned for four days and is reported to have destroyed Thirteen thousand homes. Building regulations invoked as a result (and seeking to prevent possible further tragedies) dictated that new houses had to be built of either stone or brick. As stone construction was still proving too expensive for the common majority, then most were rebuilt using brick.
Further to the bricks themselves, the manner by which they are laid gives us guidance toward the period from which they derive – with popular coursing styles and differing pointing styles being favoured across a range of time periods.
In summary, whilst we can apply the known factors detailed above to help identify the approximate period of time when they were produced, bricks have always varied in size due to the very nature by which they are produced. Even a standardised mould from a single brickmaker could produce wide variation of colours and sizes due to small fluctuations in composition, the temperature they are fired at (which can vary on each firing), and even differential temperature changes from the position where they are stacked within the kiln itself. Add to this pointing characteristics which may have been altered or replaced and you can see we are presented with a potentially confusing conflict of information.
British archaeologist Ivor Noël Hume (heralded by his peers as the father of historical archaeology) is quoted as saying “Bricks have served as a kind of Rosetta Stone for architects and archaeologists attempting to date old foundations and buildings. The sad truth of the matter, however, is that individual bricks are not nearly as informative as we are often led to believe, though when seen in their original coursing they can offer us a few general guidelines. The fallacy of trying to date a building by its brick sizes is exhibited time and again when one measures numerous examples from one foundation and finds half a dozen different sizes used in its construction”
The brick tax was a property tax introduced in Great Britain in 1784 (during the reign of King George III) in the immediate period following the War of Independence, to help mitigate the cost of the war. Bricks were initially taxed at 4 Shillings per thousand. To minimise the effect of the tax, manufacturers began to increase the size of their bricks, up to a maximum of 11” × 5” × 3½” (280 × 125 × 80mm).
In response, the government introduced a maximum volume for an individual brick, at 150 cubic inches (2,500 cm3).
This level of taxation was increased further in 1794, 1797, and 1805, peaking at 5s 10d per thousand bricks. The tax on bricks was abolished in 1850, by which time it was considered to be detrimental to industrial development and various efforts were made to standardise sizes once more. A size of 9” x 4½” x 2½” (equivalent of 228 x 115 x 64mm) was widely adopted from 1840 and was only subsequently replaced by the metric brick in 1970.