2014 Theses Master's

In-Kind Terra Cotta Replacement in the 21st Century

Barr, Emily

Architectural terra cotta was the most popular building material in America between 1890 and 1930. As an era of innovation, the characteristics of terra cotta and appropriate construction methods were not fully understood. With building construction halted during the Great Depression and changing architectural styles, demand for terra cotta dropped to a low, and the industry fell into decline, nearly disappearing completely. As terra cotta buildings began to age and deteriorate, the industry no longer existed to provide material replacement as needed. Various alternative materials were explored and used for reasons of availability and cost. However, performance and appearance of some of these materials was deemed unsatisfactory and the continued need for more appropriate replacement materials has led to a recent revitalization of the terra cotta industry.

Currently three major manufacturers produce architectural terra cotta for replacement material in historic structures: Boston Valley Terra Cotta, Gladding McBean, and Shaws of Darwen. Each of these companies uses different fabrication processes ranging from traditional hand pressing or slip casting methods, to mechanical methods of extrusion or RAM pressing. The technology and processes available for terra cotta production have changed significantly over the last 100 years. In spite of the comeback the industry is making, little research has been done to compare the current materials, production process and installation methods to those traditionally used, and how they have or can be improved.

Modern terra cotta production has incorporated new technology to: improve the quality of the product, reduce time necessary for production, lower cost and thus increase the feasibility of replacing terra cotta in-kind. With a better quality control of the production process, a more predictable and dimensionally stable terra cotta product can be achieved. It raises an important question. While preservation encourages the use of in-kind replacement, is it actually still the same material? This is not just a philosophical issue but goes to the heart of the physical characteristics and their compatibility. This paper seeks, through a review of current production processes in comparison to historic methods, a material analysis (petrography and visual survey) to examine the characteristics of current material and effects of modern fabrication processes. In addition it intends to review traditional installation techniques to ensure replacement interventions better accommodate the characteristics and capabilities of the material. This research includes a comprehensive review of the production and use of terra cotta, and effects of physical requirements, time constraints and cost considerations. This extends itself not just to manufacture but includes with the overall goal to encourage proper in-kind replacement, assure the longevity and success of the replacement material within our historic structures.