Deciding on the date of a brick is a far from simple process. The very first point to remember is that bricks are regularly re-cycled; consequently bricks may well be older than the buildings that contain them. Secondly, any attempt to date British bricks stylistically must allow for regional variations; the size of pre-18th century bricks, and their arrangement, did not conform to any nationwide standards. If you want to date your local bricks you will have to get information specific to the county or city that you live in. Several methods of scientifically dating individual bricks have been explored. The most promising is rehydroxylation dating (RHX). This technique can in fact be applied to all fired ceramics. After firing minute amounts of water slowly combine chemically with the ceramic leading to a very gradual, very small, gain in weight. This weight increase happens at a predictable, but slowly declining, rate over hundreds or perhaps thousands of years, and is easily measured. RHX dating is still subject to active research but shows great promise. But reasons of cost and difficulty dictate that, for the foreseeable future, the amateur enthusiast will continue to depend on the appearance of bricks for date estimations.
Brick and tile-making technology was originally introduced to Britain by the Romans. Recycled Roman material is commonly seen in Saxon and Norman buildings. After an interval brick seems to have been reintroduced to eastern England from the Low Countries in the medieval period. Between the 14th and early 16th centuries brick was employed solely in elite structures such as Tattershall Castle and Hampton Court. The bricks are thin by modern standards, perhaps 2” in thickness, and bright red bricks were popular in the Tudor period. The buildings in which they are found are better dated by historical records. Brick starts to appear in vernacular buildings in the mid-16th century. All such bricks were hand made in wooden moulds from alluvial clay, although bricks shrank during the firing process. Firing was undertaking in regular heaps., ‘clamps’, of bricks either on the site of the future building or at brick-fields where clay was dug. Some experts believe that the moulds show enough individuality for the work of single brick-makers to be recognised. The repeating arrangement of bricks in a wall is called the ‘bonding’. In early buildings English Bond was adopted, in which a course of ‘stretchers’ (bricks laid lengthways) alternates with a course of ‘headers’. In time Flemish Bond was introduced, in which stretchers and headers alternated in each course. A building showing Flemish Bond must be later than 1631, and effectively the arrangement dates a building to after the late 17th century.
We are now into the modern era. In the 18th century 2½” was an average brick thickness and this dimension slowly increased in the 19th century to reach 3” – 3½”. To some extent this was the result of a government imposed brick tax based on the number of bricks a manufacturer produced. After 1850 this tax was rescinded and there was no motive for making a brick any larger than could be conveniently handled by a brick-layer. Bricks slowly became thinner once more showing a slow decline to 2 5/8th inch. Machine pressed bricks were a Victorian development; contemporary architects liked a standard product of a uniform colour with smooth faces and sharp arrises. Such a brick required machine-making and kiln firing. In the mid-19th century recesses for mortar, called ‘frogs’ were introduced into brick making. Both hand-made and machine-pressed bricks could be frogged. After 1850 manufacturers began to impress their initials, names or companies into the unfired brick. A ‘brick-mark’ of this type should, after a little research, enable you to identify the manufacturer and date of the brick with some accuracy. In the 20th century large manufacturers, like London Brick Company, began to dominate the market. Large perforations through the brick fabric make firing quicker and cheaper. This is a mid-20th century development as is the use of modern Portland cement in mortar.