These, known also as brick tiles, are a speciality of Lewes and Brighton although examples do occur elsewhere in the south east of England. They were first used around 1875. Timber framed buildings which could be mediaeval in origin were, in the Georgian period, felt to be unfashionable. In order to alter the look of a building the timber frame, with wattle and daub infill, would be covered by boards on to which the tiles were nailed and bedded in lime putty or mortar. If the infill was already brick the tiles were simply glued on with the lime mortar.
The introduction of mathematical tiles seems simply a fashion choice and not a device to avoid the brick tax of 1784 since the tiles were also taxed, often at a higher rate. The brick tax was a property tax introduced in Great Britain in 1784, during the reign of King George III, to help pay for the wars in the American Colonies. Bricks were initially taxed at 4 shilings (20p) per thousand.
The tiles were made from the same clay used for brickmaking, making it quite difficult to tell the difference between bricks and the mathematical tiles. There are clues however. Corner tiles were rarely made and the problem at the corner of the building was sometimes overcome by fixing vertical boards or wooden corner stones. Similar detail occurs around windows usually lacking a vertical hung course covering lintels. Originally the tiles were red, but black and cream examples exist.