Mathematical tiles are tiles which were used extensively as a building material in the southeastern counties of England—especially East Sussex and Kent—in the 18th and early 19th centuries.[1] They were laid on the exterior of timber-framed buildings as an alternative to brickwork, which their appearance closely resembled.[2] A distinctive black variety with a glazed surface was used on many buildings in Brighton (now part of the city of Brighton and Hove) from about 1760 onwards, and is considered a characteristic feature of the town's early architecture.[1][3] Although the brick tax (1784–1850) was formerly thought to have encouraged use of mathematical tiles, in fact the tiles were subject to the same tax.[4]