Historic Markers Across Georgia

Strong Walls From Refuse

Marker ID: NPS 
Location: Fort Frederica National Monument, Saint Simons Island, GA
County: Glynn
Coordinates: N 31° 13.398    W 081° 23.364
  31.2233    -81.3894
Style: Interpretative Sign **
Waymark: None


Strong Walls From Refuse
Fort Frederica National Monument

The settlers of St Simon's Island in the 1700s used an unusual building material—oyster shells. The colonists found piles of them when they arrived here, discards from long-ago feasts of the local Guale and Mocama Indians. These mounds of shells, or middens, formed the basic ingredient of a crude but durable concrete called tabby.

(background) To make tabby, stacked logs and oyster shells, called ricks, were set afire and allowed to burn down to hot embers. The shells were burnt to ash. The wood and ash mixture formed lime. When mixed with water, sand, and more oyster shells the lime served as a binding agent, solidifying the mixture. It was then poured into molds for foundations and walls which were stuccoed and whitewashed to protect them from water damage.

(upper right) The settlers borrowed the recipe for tabby from the Spanish. The word might originate with the Arabic word tabbi, meaning a mixture of mortar and lime or with the Spanish word tapia which means a mud wall. It's a very old building material dating to the 1500s.

(lower right) The strong walls and foundations of many of Frederica's buildings are built of tabby.

National Park Service-United States Department of the Interior.