Shellcrete at the Fulton Mansion

Posted by on Jul 10, 2013 in Journal, Material Conservation
  • Fulton Mansion Shellcrete Detail
  • Fulton Mansion Shellcrete Basement
  • Fulton Mansion Shellcrete CloseUp

The Fulton Mansion in Rockport, Texas was an innovative structure when it was built in 1877.  In addition to its numerous modern amenities, a very interesting regional construction method was incorporated into its foundation, basement walls and vaulted porch floor structure.

Shellcrete (also referred to as ‘tabby‘) was a material that had been utilized in this area for many years at the time the mansion was constructed.  It was a locally adapted alternative to adobe because it performed better in the humid coastal conditions.  There are several other sites nearby where examples of shellcrete construction can be seen, such as El Copano (or click here, here & here) in Refugio County (1820’s-1830’s), the Cenntenial House (or click here) in Corpus Christi (1849), the Stella Maris Chapel (or click here) in Lamar (1858) and the Civilian Conservation Corp building at Goose Island State Park (1934).  Other examples of this construction method can be found along the Southern Atlantic Coast, as well.

Shells (primarily oyster) were not only used as aggregate, but also as a binder because of their lime content.  By slowly burning these shells over several days the calcium carbonate in the shells was converted to calcium oxide, also known as quicklime.  This quicklime added to the strength of the mixture, forming a simple concrete-like mortar when combined with sand, broken shells and water.  Click here for a more in-depth description of the process for making shellcrete.

Typically, shellcrete would be formed into blocks, allowed to cure and used as masonry units.  At the Fulton Mansion, the shellcrete  was instead poured into a formwork, and later covered with cement stucco.  Part of the restoration that is currently underway will be to repair this stucco to protect the shellcrete from deterioration.  In other locations, reinforced concrete will replace severely deteriorated shellcrete vaults.  And where this vault structure rests on shellcrete walls below, the walls will be consolidated to increase their bearing capacity.  To the extent possible we will preserve the original shellcrete, which is now almost 140 years old.