Cemesto Panels Study

Some of the many new and experimental building materials used in the twentieth century are now known to be harmful to human health. At the Eames House, the Cemesto infill panels fall into this category. These opaque panels are an important and culturally significant component of the Eames House building envelope and present some of the site’s greatest conservation challenges.

Manufactured by the Celotex Corporation, Cemesto is an asbestos-cement-encased fiberboard that was one of several insulated panels to enter the American market in the 1930s. Its popularity waned as increased awareness of the toxicity of asbestos led to progressively restrictive regulations concerning their production and use, as well as more stringent management and work practices designed to prevent exposure.

At the Eames House, this off-the-self material was trimmed and customized to fit the various configurations of the steel frame. On the exterior, the faces of some of the Cemesto panels were left their natural, soft gray color, while others were brightly painted; two accent panels above the front entry were covered with gold leaf. On the interior, all the panel faces were left unpainted.

The Conservation Institute’s investigation of the Cemesto panels was divided into two phases.

• The first phase included historical and technical research, an in situ visual condition assessment, and limited material testing and characterization.
• The second phase involves reviewing applicable guidance, understanding the limitations of preserving hazardous materials, and developing suitable conservation treatments including repair and encapsulation to allow for retention and management of the panels in situ while ensuring users’ safety. The Institute is also investigating a suitable product to replace original panels that are damaged beyond repair.

Based on physical evidence, more than half of the Cemesto panels are original and maintain a high degree of intactness but show deterioration at various degrees and are highly vulnerable after more than seventy years of service. Their conservation presents significant challenges stemming from the building enclosure design, the hazardous nature of the asbestos material, legal constraints, the limited availability of in-kind replacements, and very little available information on how asbestos-containing materials of cultural importance can be conserved, maintained, and repaired.

The outcomes of the investigation and treatment of Cemesto at the Eames House will provide a model for the treatment of these and other brands of cement-asbestos insulating panels at other twentieth-century buildings.