Structural Design of Terra-Cotta Walls

Terra-Cotta Blocks

• The terra-cotta blocks most commonly used for wall construction are hollow units with thick exterior walls and a series of internal compartments divided by a web of structural stiffeners. Their hollow design makes these blocks much lighter than conventional bricks or stone. The high temperatures at which they're fired makes the blocks stronger than bricks. Terra-cotta wall blocks are often coated with a heavy glaze finish to imitate stone or other materials. Terra-cotta blocks intended to be finished with a layer of stucco or plaster have a corrugated exterior profile that provides a better grip for the finishing material.

Structural Terra Cotta

• Although used often in high-rise buildings in the early 20th century, terra-cotta blocks are not well-suited for use in load-bearing walls in extremely tall buildings. In buildings over four stories high, terra-cotta blocks are more often used between the support members of a steel structure than as load-bearing walls. In buildings less than four stories high, terra-cotta blocks can be used in load-bearing masonry walls similar to brick or stone.

Terra-Cotta Cladding

• Terra cotta was also commonly used as cladding on the exterior surface of walls. Wall ornaments and decoration are easily cast in terra cotta, and crafting architectural details from terra cotta was much less expensive than carving similar details from stone. Glazed terra cotta could be designed to mimic sandstone, granite or other heavier, more expensive material. Terra-cotta cladding was usually attached to a metal framework anchored to walls' exterior surfaces.

Potential Problems

• Terra cotta is particularly susceptible to water damage, and because the material was once thought to be impervious to water, terra-cotta walls were often built without adequate protection from water. Consequently, historic terra-cotta walls are often subject to cracking and deterioration caused by moisture. Rusting of the metal anchoring system is also a problem in walls with terra-cotta cladding, and structural failures caused by antiquated building design or improper subsequent repairs are common.