Tabby is a building material consisting of lime, sand, water, and crushed oyster shells. It was developed and used by English colonists in Beaufort County and on the Sea Islands of coastal South Carolina, in coastal Georgia, and in northern Florida in the Southern United States. The period of use extended from the Colonial Period into the early 19th century.
The labor-intensive process depended on slave labor to crush and burn the oyster shells to supply lime. They were combined with sand and water in wood forms to hold the shape until the material hardened. Tabby was used as a substitute for bricks, which were rare and expensive because of the absence of local clay. Some researchers believe that the name came from the Spanish word, tapia, which means "mud wall", but that English colonists developed their own process independently of the Spanish.