Photo: Eric J. Nordstrom

Photo: Steve Hall & Kendall Ristau Photographers, LTD


Terra cotta commonly comprises clay-based materials, sand, and grog (in architectural terra cotta) that have been pressed and fired to create a unit masonry material. Grog is previously fired clay pieces that are integrated into the mix as “aggregates” to help stabilize the clay materials and limit shrinkage for larger units. Terra cotta units are architectural terra cotta, hollow clay tile, guastavino tiles, roof and coping tiles, and interior tile. In general, terra cotta materials use more refined and denser clay body mixtures than clay masonry brick. 

The manufacturing process varies based on how the units are formed, including hand pressing, extrusion, slip casting, and ram pressing. Because clay has high moisture content when excavated, there are several steps in the manufacturing process that allow the materials to dry, including air drying prior to mixing in a pug mill, and after forming. If the clay units dry too quickly, they are prone to shrinkage cracking. Architectural terra cotta and decorative guastavino tiles are finished with a glaze, which can be a slip finish, matt, or high gloss and can come in a variety of colors and designs. Hollow clay tile and structural guastavino tiles are unfinished. 

The information on this page primarily focuses on architectural terra cotta. Although these units are strong and dense, their vulnerability is how they are anchored and connected to the wall assembly. Where there are individual terra cotta units within a brick masonry facade, they are often set in with the mass masonry wall assembly. However, architectural terra cotta’s popularity grew between the end of the 1800s to early 1900s and were largely used as full facade cladding systems anchored back to a steel frame structure with infill walls. Historic Architectural Terra Cotta Standard Construction by the National Terra Cotta Society (1914 and 1927 editions) graphically illustrate details of how terra cotta units were commonly assembled and anchored.  


For successful historic and existing projects, it is important to prioritize repairs based on the structure’s conditions and project team goals. Project strategies differ per project and can be selected from a variety of repair options. 

Refer to our general restoration best practices page for additional information, details, and resources. Below, find terra cotta repair and restoration options for consideration on your project. 

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Installer Certifications and Training

Why settle for anything less than the best when it comes to the installers on your project? BAC craftworkers train throughout their careers to become building enclosure experts and masters of their craft. 

When you want to have confidence that you’re working with qualified, experienced crews on your project, you can specify for well-trained craftworkers.

Here are some of the training, certificate, and certification programs you may want to specify for terra cotta construction. 

Historic Masonry Preservation Certificate Program

Traditional craft skills and contemporary repair techniques are critical to the preservation of historic buildings and structures. This in-depth certificate gives BAC craftworkers integrated knowledge of historic masonry preservation.

Terra Cotta Installation and Repair

The skill of qualified craftworkers is essential for a successful historic and existing project. This program provides an in-depth look at terra cotta as an architectural cladding material, its manufacturing, overview of its performance, and methods of repair.


Here are some additional resources that focus on terra cotta and restoration. For a more comprehensive list of repair and restoration resources, please refer to the restoration page. For additional guidance, contact IMI.


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